My .02
For the day to day things, Windows Phone will be the most pleasant (more so when Mango comes out, mainly because of multi-tasking)
Hardware isn't as nice, but it isn't bad either. If you are in no rush, you could see what new phones come out this holiday season.
Apps are decent, but the marketplace is still young. You can find an app for just about everything, but the polish/function may not be up to par with the Apple version. In some cases this is the opposite though. Either way, post mango apps will really be where the app marketplace gets good, because of all the many much needed API's that MS opened up to developers.
Plenty of good games. Much of the same situation though as with the apps. But the xbox live ecosystem is nice, and will only get better.
So I think you will have a few pains in switching, but the day to day tasks you might find more enjoyable on your Windows phone. And as long as you have some patience, the phone is maturing at a break neck pace, so in no time at all, you may not miss anything from your iPhone at all.