If for some unexplainable reason you're not sold on WM6 yet, you might want to take a look at this Reference Guide PDF Microsoft has just released. It's a 61 page document that goes over all the new features of WM6. If you're trying to convince your company to upgrade your devices to one of the great new phones coming out in the next couple of months, this PDF would probably go a long way towards convincing your boss.
Going through it, I'm starting to understand why Microsoft calls it WM6 instead of the WM5.5 that many people believe it should be called. Sure, it's based on the same core as Windows Mobile 5, but the sheer number of new features justifies the uptick in the version number. Give it a download and start salivating.
Here's a handy reference guide that illustrates the new features of Windows Mobile 6 as well as the reason for the new naming convention.