I love my iPhone 4S, and I'm pretty fond of iOS, however I love WP7 as an OS, and have been toying with the idea of making a switch to WP7 for a while now, with the imminent release of the Nokia Lumia 900 the temptation has never been so strong. One of the biggest things holding me back so far has been that I've invested a fortune into the iOS app store, but if the experience of WP7 is worth it I may be inclined to make the sacrifice. To anyone that has made the leap from iOS to WP7, what was it like? What do you love or hate about WP7? Was it easy making the transition and learning a new OS? Would you recommend it?