It's a HUGE learning curve - it's the first time in years that I've really had to hunt to find things in an Office product upgrade. I have seen some tools rolled out whereby you can go through a faux Office 2003 screen to select an option, and it shows you where the corresponding option lives in 2007.

Getting used to it now (and I do like some of the new features) but my biggest frustration is with the ribbon. Their policy appears to be "I'm going to guess what I think you want to do next, and make the ribbon that you actually want (and hunted for 5 minutes to find) disappear again". I'd love to switch this off (if I could work out how to do it) - contrary to Microsoft's opinion I generally have a slightly better idea of the functions I need to access next then they do!