Fancy new cell phones

So I'm thinking about replacing my dinky old motorolla flip phone that Jenn and I both got about two and a half years ago. The front runners at the moment are the Sidekick II and the Treo 650, though it appears with the Treo we would have to jump ship to another provider (not that it's a huge deal, but one more thing to worry about). I think T-Mobile used to offer the Treo, but I can't find it on their site anymore. I suppose I could try and snag an unlocked one online somewhere, but I haven't a clue what type works with which service and so on. Plus it seems like the unlocked ones are significantly more expensive.

The big thing I'm looking for this time around is synchronizing with at least one calendar source. My work calendar is the most important, but if I can work in a personal calendar (possibly on another machine) that would be nice. Web browsing, instant messaging, ssh clients, and so forth are nice bonuses but they aren't have to haves.

The main pro for the Sidekick at the moment is that it is the cheapest option from what I have seen in my initial research. Since we are already T-Mobile customers, we can get the "upgrade" price for the Sidekick if we extend our contract another two years. And the monthly cost for the family plan plus the data service (unlimited, but that was the only option) is under $100. It's actually about the same as what we're paying right now (we're actually overpaying a bit on an older plan). Comparable plans with other providers were all over $100/month.

(And the fact that the SDK for the Sidekick seems to be easily available and Java-based, which is what I work with at my day job, might be fun if I have the time to tinker with it, like that will actually happen.)