Announced about a year ago, the SD Card Association's SD 3.0 specification has yet to gain much traction. Panasonic and Toshiba both announced UHS-I SDHC products last September, with Toshiba claiming ultrafast write speeds of up to 80 megabytes per second. But those cards have yet to materialize. At CES 2011, Kingston announced a new series of UHS-I cards, unfortunately dubbed UltimateXX, with a claimed 35MB/sec write speed and slated to be available this month. SanDisk now ups the ante, expanding its Extreme Pro line of of flash cards from CompactFlash to SDHC, with the momentarily fastest spec of up to 45MB/sec write speed, It also has a video-rated minimum sustainable write speed of 10MB/sec.

You're definitely paying a premium. Prices range from $109.99 for the 8GB card to $349.99 for the 32GB card. In contrast, you can get the 30MB/sec version of SanDisk's 32GB card for about $170. Which raises the question: what kind of speed boost does that extra dough buy you

Well, if you don't have a Nikon D7000, not much' for now, the only camera which we know of that supports the UHS specification is that one. So I popped the 32GB Extreme Pro into the camera and took it for a continuous-shooting test drive. I compared it against the fastest card I happened to have lying around, an 8GB 20MB/sec Extreme III.

As a reminder, faster cards don't actually increase your burst speed (unless your current card is exceptionally slow). What they do, in theory, is allow the camera to save out the images cached in the buffer faster. That effectively gives you a higher burst rate once you've passed the buffer depth--in my case about 18 fine JPEGs, 8 raw/raw+JPEGs. What I've found when it comes to card speeds, though, is unless the card is fast enough to allow the camera to empty the buffer by a significant amount, the burst still slows too much to be really useful. For shooting JPEGs, the Extreme Pro did increase the effective burst rate, enabling 5 extra shots within the same time interval. For raw+JPEG and raw, though, it gained maybe one shot before the buffer bottleneck kicked in. And that's compared to a card that's not even close to the currently fastest available.

It always pays to have a faster card when it comes to downloading, though, and the card's maximum 60MB/sec read speed certainly can come in handy for that' it's not unique in that respect, however, as quite a few cards offer fast read speeds.

So if you shoot with a D7000 and need fast continuous shooting relatively far into the buffer, the Extreme Pro may be worth the extra money for you. But don't expect the same results with raw or raw+JPEG.