Theres a lot. 720p video recording, 4G speeds, HTC Sense, ability to turn off sense, massive screen, Sprint's cheap plans, and so on.
If I had to choose one, it would be the 4G speeds. I use the browser the most on smartphones, so that extra speed will be amazing and automatic HQ videos on YouTube. Bad-ass.
PS: My birthday is on June 1st. Would be something to win.