Purchased my Pico 8Gb USB micro pen drive one month back and currently using it to boot Ubuntu 9.04 on to my laptop. Performs exceedingly well with Ubuntu booting to a usable desktop in under 40 seconds, far quicker than Vista.
As many have said, it's really small so would be easy to loose when not plugged in to my laptop, just remember the saying "A place for everything and everything in its place" and keep to it. Secondly as a previous reviewer mentioned it would have been nice for it to have had an activity LED.
In summary, an exceedingly small, well executed, and super performing USB drive. Highly recommended.