It's generally inoffensive, and there are some interesting enhancements (such as the option to see more detailed info when you are doing a mass file copy). "Show me all the options" buttons are everywhere in the control panels -- a nice nod to the fact that not all of us need the stuper simplified menus. The basic security model also seems to be more rational than Vista's out of the box stance. And it's very pretty.
That being said, pretty doesn't get any work done. In the end, I didn't find anything particularly compelling about it. As many of us in IT have become accustomed to thinking about Microsoft at least it doesn't break a lot of things that are working fine now.
This really is a product that's all about maintaining a revenue stream, not about technological advancement. To-wit, someone has crafted a desktop theme for XP that makes it look like Windows 7 beta's default Aero theme. Everything I saw in Win 7 that I liked could be provided in XP in "XP SP4". Then again, this is all about revenue. So, I'll probably have to look at this again when work adopts it. At least it doesn't break a lot of things that are working fine now.