I just upgraded from Quicken 2006 Premier for Windows to 2007. My initial reaction is they did great things to the user interface. They fixed some things I did not like in 2006 like fixed column widths in the scheduled transactions area, and I really like how it shows the "downloading" animated icon next to each account that is still being downloaded. That's a nice touch.
Overall first impression is an awesome improvement. Of course I'm only commenting on visual improvements. We'll see in a couple of weeks when I get a bit more familiar with the other changes.
Scott