I didnt't seriously start using Excel until the 2007 version, but I must say that the Ribbon is much better than the old system. The discoverability of keyboard shortcuts are much higher when you only have to press the alt key to reveal them.
Of course I also use some other shortcuts that are not on the ribbon, but that's just a bonus.
Of course I also use some other shortcuts that are not on the ribbon, but that's just a bonus.