I've got a Corsair, a couple of Emprex brand, and a couple of Sandisk Cruzers. I would recommend all of them! As far as the U3 goes...I've left it on both Cruzers, so far. I like the built in anti-virus. You can scan any computer you plug it into, which comes in handy when using friends' computers that you just know are loaded to the hilt with crap! Some people still aren't sure if they really need anti-virus or not! I have run into a problem with the U3 drive, however. It doesn't work properly if you've got NetFramework 2.0 installed. (I think it may not have worked at all.) I ended up uninstalling NetFramework 2.0 (which was needed to run a certain application). I even think NetFramework 1.1 makes it so that the U3 software doesn't load automatically, sometimes (most times?). That's ok, though, because the drive is still fully functional with NF 1.1 (needed to run another particularly useful app).
Read/Write speed is something you might want to look into. They're not all created equally.