If you're thrilled by dual-core processors, extremely high-res screens, large camera sensors, customizable widgets, expandable storage, USB mass storage and other such features, then you'll be better off with Android or -- to a slightly lesser extent -- iOS, because that cutting-edge stuff is currently absent on Redmond's OS. On the other other hand, if you want to be part of a carefully crafted, simple and generally happy emerging ecosystem, then look no further.
ENGADGET: Nokia Lumia 800 review Mobile