I've been using Windows Phones for a while after using iPhones for a while. The (former) Nokia hardware are solid and the entry level devices are being given away. Check out Cricket -- they are on the AT&T network but can't advertise it.

My basic take is that, so long as you don't have a big interest in Apps, it is a better device. It makes full use of the real estate and feels more like an integrated platform than a collection of functions.

But the App situation is still a mess -- no one builds for it. If you have anything you really want, check in advance.