Smartphone for Sean

With all the talk of the iPhone the past few days months, I've started to look more seriously into getting a smart phone. As I've stated before, the iPhone is completely off the table. I'm looking for something that:

1. Won't cost me an arm & a leg to buy.
2. Has a good data plan & cell plan (or a combo that is fairly competitive)
3. Will allow me a lot of functionality on the web

With those condition stated, I'm wondering what the Mod-Blog community thinks is the best option - Blackberry, Sidekick, Treo or something else that I haven't even looked at? Discuss...