Kindle... Later Cybook and iLead. Then MobileRead. Now I don't know!
Kidding. Right now I'm inclined for the Cybook, although Heinlein V3 got me intrigged, specialy with zip and rar support (BeBook doesn't have it, I've asked). I'm also curious about Astak, but I guess it will take a few months for the 6" model release.