@ John Robson
"""PCIe ssd should be released in expresscard format as well..."""
Actually there are plenty of expresscard ssds out there, most of which you could probably even boot from. The problem is that the format is too small (and too low power) to fit a decent amount of flash, lots of cache, and a high end storage controller. Plus they aren't any cheaper than 2.5" internal SSDs, so you might as well just slap one of them inside your computer and save that express card slot for something useful. Possibly store paperclips or toothpicks in it...
And for years PCIe motherboards have been able to boot from PCIe storage controllers, but as mentioned, I only see that being useful if the Gamer or Workstation versions have reasonably small capacities. I really hope I don't run into too many morons that think they need that much high speed flash storage to play Farcry 2 or make a youtube mashup.
Yes, as mentioned, random write is the all-important factor in these flash drives. If these PCIe deals are as high quality as they sound, they'll have a fair amount of DDR2 cache, and a battery unit, so you can safely cache writes. I'm not saying that is a perfect solution, but it could at least boost write speeds until the cache filled, and with a proper controller it could make for more efficient writes. A sequential read speed of 250MB/s is great and all, but not when you have to take a 6MB/s random write speed along with it. Which is the only reason I don't own a couple SATA SSDs by now...