I just switched to Ubuntu for my home computer last saturday, after 15 years of using pretty much every version of Windows. I'm not new to linux on the server-side, but very new on the desktop side.
After playing with it for a couple days, I don't see a single piece of innovation. The effects when moving the windows are neat. The package-management GUIs are useful. But that's it. There's nothing in there that isn't on other OSs. So I don't see where the innovation is.
On the other side, there are many little glitches, many little weird things that make Ubuntu (which IS the "linux Desktop" right now) not as good as Windows. Nothing important, nothing blocking, but annoyances that no other OS wouldn't fix.
For instance the fact you have to hit the "number lock" key every time you're on the "input your password" screen...there's most likely a fix for that, but then why (and how) would a basic user have to fix that ? There's more, like when you try to find out what's wrong with your sound card, or when your keyboard switches from your setting to another when you start some applications. And there's the copy-paste thing, where the copy part works great but the paste part needs you to figure out if the current app needs you to press the right or the middle button, or in a few cases ctrl-v.
The Linux Desktop is probably the greatest chance the world has to get away from MS and Apple one day, but right now, as a user, I have to say it's not ready. As 10+ years linux supporter I would love to say it is (even slightly) innovative, but it would be a lie. Right now, it can't really compete with other OSs, seeing how every app beahave in their own way. And you can't call that innovation. MS and Apple got this straight for a while now, probably because it's what matters to the user, even more than the fancy effects.