Now I've spent a few hours digging into the Android developer site. While I have some concerns, Artem makes a very good point: this is a platform that developers want to develop for. There's a public SDK a good 6 months or so before the first actual device will be released.
Sure, people seem to want to write code for Windows Mobile as well, but Steve Ballmer is like the only person in the whole world who would consider Windows Mobile a success. Symbian has 70% of the worldwide smartphone market, and that's starting to translate into a serious share of the mobile phone market as a whole. The most recent figures I saw are that 7% of the mobile phones being sold at the moment are running Symbian OS. Where does that leave Windows Mobile? 0.4% or so. About the same as Apple, that have been in this business for a couple of months now. Way to go, mr. Ballmer!
Speaking of the iPhone, there's a device that people want to write code for, and soon there will even be a public SDK. Of course, we don't know much about what sort of openness they'll provide yet. Sure, you might have the SDK, but there's no guarantee that you won't have to shell out a few thousand currency units to get you app signed, so that it can actually be installed.
There are some concerns about the Java emphasis of the Android platform. The problem I see with this is that there's no way to do a five minute port of your existing app if it's written in C. About performance, I don't think there's a reason to worry. You can write kick-ass games that run on VM:s, as long as they're done right. This was proved a long time ago with mophun, and when actual Android devices are on the market, most phones are going to have 3d hardware. For DSP stuff, there might be a problem, but it's not like there's a lot of DSP related apps around for the open platforms we have right now...