MS screwed up really badly with Office 2007, it forced a pointless UI on users without the usual option to use the older one. Why? Damn good question, and I have no clue as to the answer. More importantly, they put in a pointless new file format to lock out competition. This one means headaches for anyone using the new suite.
I don’t agree with all of the comments made here because I personally like the new look of Office 2007. I do agree wholeheartedly that the new file format is a pain. I’ve only used it a few times but have run into bizarre issues each time. It doesn’t help that you can’t share the files unless your friend/business partner has Office 2007 as well.
Source: The Inquirer