Changed to Visio 2010 very recently, I use it on a daily basis and now I have my head around the ribbon, I can work faster than I did with 2007, but as you see from other posts did have some issues with crashing which Windows 7 has found solutions and it appears now to be stable.
The other concern which bugs me is the zoom, it seems to be fixed to 1000 as a default which I am unable to resolve, and yet some old drawings created with 2007 version will zoom to 2900. I have attempted to change the zoom and set my own, but it skips back to 1000, which I feel limits the depth of detail I can work with, if anyone has worked out a way to change and set the default I would be very interested to hear from you.
I do not think they have made a bad job with this version and the the quick access toolbar gives a more flexible user option, I wonder how much notice they ( Microsoft) take from users prior to making changes.