Buddy!! First welcome at GS.
2ndly I am working for Vodafone at their prototype testing area. I hope you know what does prototype mean!
3rd I have used Windows Phone 7
4th A great Os is that allow you to have upgrade on the old handsets too.
5th Windows Phone 7 has somehow different Application back end and so the old application supporting Windows 6.5 or older will not have 100% compatibility with Windows Phone 7!
6th Dont underestimate people around you! 