I love my PQI 4GB Cool Drive U339 Pro. It is very fast, inexpensive, and lives in a tiny, compact case. (Note that other PQI models may be much slower than the "Pro" versions). The only drawback is that it mounts as two drives when connected to a computer, one being a read-only partition with useless "USB Notebook Software." I *hate* stuff like this. Anyway, a couple of weeks ago, the drive started behaving strangely when connected to my computers, and it finally died on me a few days later. I contacted PQI support, who recommended that I download and run a Windows-based repair utility. The repair utility seems to have repaired the drive, and as a bonus, it also removed the second partition with the useless software. So if you own one of these Cool Drives, you might want to run the repair utility even if yours is in perfect working condition! (I take no responsibility in what happens, though -- the decision to run the program is yours alone.)
UPDATE: Another cool thing I did was install Mac OS X on a partition of my flash drive and install Disk Warrior on it. So now, if my primary drive(s) fail while I'm on the road, I can boot OS X from flash and try to repair things.