Despite Steve Ballmer himself apologizing for the delay of Window Mobile 7 a few days ago, there's a lot in WinMo 6.5 that Microsoft should be proud of. Overall the OS itself has been tweaked a lot for performance -- I've tried devices that were running WM 6.1 and were upgraded to 6.5 and there's a dramatic difference in speed. Microsoft has also worked hard to make the new OS much more finger friendly, with UI elements that really required a stylus in the past much more usable with a finger instead. There's also some nice integration with new services such at the marketplace for mobile applications and MyPhone synchronization.
That's all well and good, but it's one device that I've had the chance to use for just a few minutes that's really affirmed my view of Windows Mobile viability, and it has me very excited about the platform. It's the new standard for Windows Phones and it's pretty much the device that every other Windows-powered phone is going to need to live up to. It's called the HTC HD2 (code named Leo) and it's a game changer in my opinion.