I just recently bought a 4 gig Sandisk Cruzer Micro off Ebay for about $100. Unfortunately for whatever reason it arrived corrupted. Really a pity because the thing is so damn tiny, it's awesome. I'm in the same dilemma now myself, what drive to consider next that's actually reliable. I was considering the Kingston but read some problems where they draw a ton of power upon insertion and could surge the USB ports.
I do kind of wonder though if there's any inherent problems with packing so much RAM into such a small chip. i.e. are 4 GB flash drives more likely to get corrupted than 1 gig drives? Makes me hesitant to try another 4 GB flash drive.