You know, sometimes you just have to accept change -- even if it's more painful, at first, than not changing.
I was once employed by a brick-and-mortar retailer. We used an OS/2-based point of sale (POS) system that was essentially 100 percent text-based. You pressed function keys to engage specific tasks, like ringing in a sale or a return. I was eventually tasked with writing a new POS, in-house, and entirely from scratch -- for Windows 95. Unfortunately, the main business goal was to minimize impact -- so I essentially had to eschew this great GUI-based environment and resort to having people press function keys.
The moral? Sticking with an old paradigm for too long holds back functionality. It was years later than a successor developer was able to break the mold and finally create a real GUI-based POS, which was easier to use, easier to train new associates on and so forth. It also offered better transaction models, making for faster checkouts and happier customers, and the ability to more easily integrate new initiatives like gift cards and whatnot.
A new UI like the Ribbon can obviously be painful. Windows was painful for its first DOS-accustomed users. The Start menu was painful for Program Manager adherents. But, as readers Mike, Randy and Heidi point out, once you get used to it it can be easier and more productive. Heidi, in particular, is dead-on: Office's old toolbars had grown entirely too cumbersome as Office's functionality began to require an increasing number of them. Office was overdue for a fresher UI concept, and as professional technologists we should really just get on-board.
Personally, I'm not a big Ribbon fan myself. My next version of Office (Office Mac 2010) is Ribbon-ized, so I'll just have to get used to it. I'm sure once I do I'll be just as happy with it as I am with the current "Inspector" UI approach.