I gave the Unity desktop that shipped with Ubuntu 11.04 a try. And I didn't like it much. When I heard that the 'classic' Gnome desktop (most features of which I didn't use) was being phased out, that prompted me to switch to xfce. Fortunately, that is easy to install with Ubuntu, though I had a few hiccups there too, mostly fixed by uninstalling some gnome packages.
I've got my terminal windows, browser, PDF viewer, and that's mostly it.
I don't think the problem with Gnome3 or Unity is that it's hard to switch back, is that they are incomplete prototypes that are being forced upon us to replace a mature and time tested platform. What is really wrong is that canonical is releasing glorified betas as major versions, hopefully 12.04 LTS will be an actual release.
Pff -- the Gnome community has been continuously following Windows' path, ever since forever.
You should learn more from OS X -- it doesn't matter if your system behaves or not like Windows, like if it uses the same shortcuts, if the dialogs have the same buttons and so on.
What really matters is stability, reliability, user-friendliness AND some eye-candy and visual effects sprinkled here and there, but not too much (like wobbly windows - who the hell thought that was a good idea anyway?) ; And if you don't have reliable drivers, then you're better off not going with visual effects by default.
What does NOT matter is efficiency and change for the sake of change, or useless visual effects that are adding to the pile of bugs that are already there.
Really, I'm afraid to install the latest version of Ubuntu -- I'll probably stick to the current one and just ignore its current awful bugs (like my webcam image being up-side-down in Skype, because of a kernel bug that is still not fixed, for which I should fix a file somewhere and recompile the kernel), or my wireless connection continuously dropping like it's hot.
Or maybe I'll switch back to Kubuntu or something; maybe KDE 4 is finally stable -- also, it's ironic that Gnome hasn't learned absolutely anything from KDE.
And if you still want to learn something from Windows, why don't you look at how popular XP still is. Or how about backwards compatibility which really matters to normal people.
I used to believe that Ubuntu will take over the world. I changed my mind whenever I installed a new version.
In GNOME the fallback mode is really a fallback. You aren't supposed to use it, like the safe mode in Windows.
And you don't need to - the interface is really easy to use with a cursor pointer (I use at different times a mouse, a track-point and a track pad) and there are shortcuts, which you can modify easily if you want and add new ones, too. For example I press the ThinkVantage button to bring me a terminal window.
GNOME 3 is almost perfect for me. I've never liked a window manager better than its gnome-shell - its both very expressive (shortcuts, simple tiling behavior, mouse+keyboard collaboration, 3 different ways of window switching behavior - a dock-like thingy, an expose-like thingy, workspaces and shortcuts) and you can do lazy maneuvers with the mouse. I'm not familiar with anything that comes close with that combination and simplicity and sophistication.
I'm not sure whether providing an easy fallback is the right way to go. I'm not even sure whether providing any fallback at all is a good idea.
Face it: Either you are convinced of the UI that you just created or you are not. If you are and if you are sure that it's very easy to learn for a novice user, then there's no reason to provide the fallback because wether the user is a novice or an old user - in any case, the new UI will work better, so users are better off.
Providing a fallback puts a burden on you and other developers which now have to test the application in both modes (assuming the application works in both modes - like in gnome/unity).
On the other hand though, if you believe that what you have done isn't absolutely perfect, then better not change anything and refine your work until it really is perfect.
Providing a fallback is the same thing as the dreaded "I'm an expert user"-buttons the overly complicated UIs of the late 90ies were providing.
The GNOME 3 fallback is comparable to windows safe-mode:
- video effects disabled
- is supposed to be used when correcting problems
- there aren't any improvements to it - no desktop icons, no panel applets. Just the necessities.
So it isn't really a compromise in vision or a competing interface.
I've got my terminal windows, browser, PDF viewer, and that's mostly it.