I've had a Blackberry 8900 for 18 months, with T-Mobile, and I've been eligible for upgrade, with contract extension, since April. I considered the Nexus, but decided against it. If the Blackberry 9800 had come to T-Mobile I might have tried that.
Or I may get the G2 tonight. It looks like what I've been waiting for: Decent but compact physical keyboard. Good sized screen, without being so huge and high-res as to suck the life out of the battery. Good camera, I think.
Before the 8900, I had SideKicks for almost four years. I liked the SideKick UI a lot, but I didn't like the locked-down app platform, or the frequent service interruptions. One of the developers of Android is the same person who helped develop the Sidekick, and I think Android retains all of what was good about the Sidekick, plus a lot more, of course.
I like the 8900, and it has been pretty reliable, if you don't mind having to reset it frequently and put up with quite a lot of lag. I don't know if the upgraded Bold, the 9780, will come to T-Mobile or not, but I feel that it's time to move on.
Ubizmo