I've just gotten the Treo 650 with Cingular, it is a great machine - I'm surprised to like it even more than I thought I would. Cingular's edge network gets me an avg of 100kbits/sec download speed from my apt (the only place I've checked the speed tester), which surprised me (I thought I'd be getting modem speeds at best). The full browser it comes with does a pretty decent job of rendering web pages (I mean, how good can some websites be that are optimized for 800 wide), I mostly download w/out images and the speed is perfectly useable.
The best thing I got was chatteremail which provides a ton of options for downloading your email - I use IMAP idle which gives me my mail effectively in realtime. It's pretty amazing how well it works.
The keyboard is small, but I've definitely gotten used to it already and am gaining proficiency as my fingers start to remember where all the punctuation keys are.
I gotta say, it is a great piece of gadgetry, it does reset itself, seemingly regularly, but since it starts up right away and reconnects to everything, it's sort of like having a minute of downtime once or twice a day, which I can live with.