I could not resist, and installed both :) I am very pleased with Office 2007. I think is the best release of Office I have ever used! The ribbon is great, although there are some command that are “misplaced”, but I think this is my opinion and it is based on the use I do of Office (Word, in this case). Everybody uses Word or Excel in its own way, so the Office team had done a great work examining usage patterns, correlations between command usages and position, and so on. Just read Jensen Harris blog; as an example, I found particularly amusing his post on “command lingering”.
I used Word, Excel and PowerPoint for about a month now, and I have to say I really like the ribbon, the mini-toolbar, even the Office “Start” button I initially feared so much. And it looks great on both XP and Vista too! I have found myself using and discovering more and more office commands, that I am sure where there even before Office 2007 but were essentially “ghost commands”, buried into menus and not readily accessible. A really great piece of software, even in the Beta version.