I've never been a fan of closed ecosystems, so an Android phone is probably next for me once my contract with AT&T is up or I get more sick of my Blackberry Bold than I already am.
Two things Apple fanboys need to understand (but won't)
Closed system != quality
Open system != quantity at the expense of quality
Two things Android fanboys need to understand (but won't)
Open system != better by default
Closed system != evil
WM7 is looking to be just another closed system like the iPhone, so I'm not going to consider it unless something truly extraordinary about it (or devices it's used on) comes along.
I always look at the demo models in carriers' stores for insight into how the device will age. To that end, I've ruled out any slider phone, including the Moto Droid, and any phone with a trackball; any mechanical points of failure. So, will it be the Incredible or the EVO 4G or something else? Not sure.. haven't played with them in the store yet.