When the Ribbon first appeared (in a radical redesign of Office) I heard relatives and friends say they "didn't like the new Windows". They didn't even realize at the time that only Office had changed, not Windows. The upgrade was being forced on them by their workplace IT departments.

That's what it boils down to: people don't like it when change is forced on them. It's one thing if you see a cool new product on a shelf, choose to buy it and are happy to try something new; it's quite another to have your existing products keep changing.

This is human nature. And that's why Microsoft is insane to radically change Windows; they're going all "new Coke" on their cash cow. If they really wanted a new product then they should have created a new product: new name, new marketing, new everything, leaving the existing product alone!

This problem isn't limited to Microsoft. I've been disappointed by several iPhone app purchases for instance, as companies keep "improving" their apps with updates and occasionally destroy the essence of the original that I liked so much (e.g. maybe they mess up the UI so it's not as good, or they add in-app-purchasing crap). That's not the way to treat existing customers. Sometimes products should just be left alone.