The scene just before sales for the first iPad kicked off last April at Apple&39's flagship store in San Francisco.

Mock them or envy them, you can expect more than a few gadget aficionados to be lining up at Apple stores today to buy the new iPad.

The overwhelming success of the original iPad ended up taking Apple by surprise last year, with the company announcing sales of more than 300,000 Wi-Fi iPads on its first day, going on to hit 1 million in just under a month. Over the following months, supply was scarce, with Apple resorting to a reservation system that would have users waiting weeks in some cases. This ended up affecting Apple's plans to release it outside the U.S., causing sales in nine other countries to be delayed for about a month.

Things look very different this time around. With the second generation of the iPad set to hit store shelves this evening, analysts are already betting it will hit the million unit sales mark faster than the first. Now about those differences:

A pre-order receipt from the first iPad.

No pre-orders or reservations With the first iPad, buyers could pre-order, or reserve the device from Apple about three weeks ahead of when it actually hit store shelves. That meant people who had pre-ordered would get an iPad delivered to their door the day it was released or walk into the store on launch day and be guaranteed a unit. This time, online orders have been restricted to the first day the device is on sale (which started three hours ago to be precise), with orders going out to customers the following week.

This could end up having a dramatic impact on the size of lines at retail stores, given that people who might have wanted to grab an iPad 2 to use it that first weekend will have to head to a store to get one versus waiting for it to be delivered to their doorstep. At the same time, it could also simplify the line-up process at a number of stores. For the first launch, Apple had to balance out two different lines: one for walk-ins and one for people with reservations.

More retailers Following up on that last point, the iPad 2 is being sold at more stores from the get-go. When the first iPad launched, the only place you could get it was Apple and Best Buy's retail stores. Apple later extended its retail availability to Target, Wal-Mart, Sam's Club, Verizon and AT&T retail locations, and online at Amazon.com.

This time on day one, the iPad 2 will be available at Best Buy (as it was before), but also the rest of those retail partners, with the exception of Amazon.com, which has not yet committed to having the iPad 2 on sale. The online retail giant declined to comment on its iPad 2 sales plans. Considering Amazon currently carries a number of Apple products, including the first-generation iPad, it's a safe bet it will end up on there eventually. Though Amazon's knock at the iPad's usefulness as an e-reader in an advertisement from back in September could have put the retailer on Apple's naughty list.

More countries The original iPad launched in the U.S. on April 3, 2010, with the promise that it would arrive in a handful of international markets by the end of the month. Less than two weeks later, Apple announced that it would be delaying that launch until the end of May.

The international launch came to nine additional countries on May 28, with Apple opening up for international pre-orders on May 10. Two months later, availability expanded to eight more countries. China then got it in September, followed by Malaysia in November, and India at the end of January of this year.

This time, the iPad 2 is still launching in the U.S. first, but 26 additional countries will get it just two weeks later. In its initial press release about the iPad 2, Apple said the iPad 2 would be available in "many more countries around the world in the coming months."

That quick increas to include 26 countries within weeks of the U.S. launch is a good sign Apple has been stocking up to make sure supplies won't run as dry as they did during the launch of the first-generation device. Even so, reports had cropped up in early February that Apple was just beginning to mass produce the iPad 2, giving the company little more than a month to build a launch supply.

An iPad 2 with the 3G antenna.

3G from day one There was a nearly one month delay between the release of the Wi-Fi-only version of the iPad, and the one that shipped with a 3G antenna. This effectively split up the number of people who would have queued up in front of stores to pick one up.

Yet lines were formed. While not nearly as large at the ones for the Wi-Fi-only version, people set up shop outside of Apple stores and waited for 5 p.m. to hit in order to get their hands on a version of the device with built-in 3G.

This time, all three models will be available with a 3G option, in addition to a choice of 3G carrier, which in the U.S. is AT&T or Verizon. Since the two are using separate types of network technology, users have to pick which of those two carriers they want to go with.

More choices Choosing between models of the first iPad was a rather simple affair. There were three capacities, and each one of those had a Wi-F-only model, and a Wi-Fi + 3G variant. But at launch, there were just the Wi-Fi units. Now, for each of those capacities (which remain unchanged), there's not just two color choices (black and white), but you can also get each capacity with 3G in either a GSM or a CDMA antenna. All told that adds up to 18 different models.

Looks are a bit deceiving on this pricing matrix. Each of those models has two colors, and the models with 3G can be had on either Verizon or AT&T, totaling 18 different types of iPad 2.

Confused as to which one to get You're probably not alone. This is actually a highly unusual amount of stock variations for Apple to offer on any product. On the Mac side, for example, you can only get one version of the MacBook, and five variants of the MacBook Pro (across three different screen sizes). The MacBook Air comes in two sizes with two different configurations per size. The iMac line follows a similar configuration lineup with two different sizes, and two configurations each. And rounding it off is the Mac Mini, which comes either a consumer version, or an optical drive-free server version, and the Mac Pro, which has the same case, but ships with four different internal configurations. None of those even gets close to the potential configurations for an iPad 2 buyer.

On the iOS side of the product line it's much simpler, with there only being three versions of the iPod Touch--all differentiated only by capacity. This is followed by the iPhone, which comes in only one color, has two capacities, and can be had with either a GSM or CDMA antenna, totaling four possibilities. (Note: Apple had originally intended to offer a white version of the device, but ran into manufacturing problems. It's now rumored to be arriving in April.)

Apple CEO Steve Jobs announces that there are now more than 65,000 native apps designed specifically for the iPad at the iPad 2&39's unveiling earlier this month.

More apps Those looking to get their hands on the original iPad did not have all that many iPad native, or universal apps to look forward to when first picking up the device in its launch time frame.

Original estimates put availability around the 3,000 mark the day after the device's release, with Apple offering an official tally of 5,000 apps at the end of May. Apple's best promise at the time was that the device would run "almost all of" the 140,000 or so apps in the App Store while developers worked to make some existing applications universal.

Fast forward to today, and we've got what Apple says are more than 65,000 native iPad applications that make up a part of the 350,000 total apps available in the App Store. Apple has branded this release with a similar promise that "almost all" applications will be able to run on the iPad 2.

One more thing... All these things combined add up to a very different picture from last year's launch, and put the iPad 2 at a considerable advantage at topping the first iPad's sales numbers. Even so, there's another big difference worth mentioning, that was not present during last year's launch: competitors.

When the first iPad launched, there were a number of Windows-based PC tablets, though they were aimed mainly at business users and packed higher price tags. There was also the JooJoo, which crashed and burned before the iPad even hit store shelves. Since then, there's been some serious movement in the tablet category with a laundry list of heavyweights like Samsung, Dell, Hewlett-Packard, LG Electronics, Acer, Asus, Research In Motion, and Motorola offering--or at least promising--to ship competing products.

While Apple's CEO Steve Jobs called these efforts "copycats" at the iPad 2 unveiling earlier this month, they do offer potential buyers alternatives. And even if a large number of them can't beat the iPad's price or massive software library, it doesn't mean competitors aren't beginning to offer things the iPad doesn't have. RIM's upcoming Playbook for instance, will run Adobe Flash, while HP's TouchPad (due this summer) will let users wirelessly transfer files between PalmOS devices, as well as pick up phone calls. Both also feature front-facing cameras for video chatting, one of the iPad 2's headlining hardware additions.

Are features like that good enough to sway buyers to put off buying a tablet until release Perhaps some, though not the ones who are sure to line up outside of Apple's store today.