iPhone 5 to Lumia 920

So after being an iPhone owner since the first generation of iPhone, I think it's time to try something new. Since I really don't like Android, I'm considering the Nokia Lumia 920. I played around with the phone a bit at the Microsoft store and I like it. That being said, I'm still a little worried about the lack of apps and overall change from iOS to Windows Phone 8. I'm an Apple guy and I feel like this is going to take a lot of getting used to.

I figured members of the "Microsoft Tribe" could help me out a bit. What am I lacking/gaining from switching to Windows Phone 8 from iOS. How well is the phone going to play with my Mac?

Thanks guys.