The GNOME 3 thing is only forced on you when you perform a version upgrade. I think most people are already aware that many things can change significantly, for better or worse, during a version upgrade. That's one of the reasons I'm still at Ubuntu 10.10.
Also, I'm certainly aware that regressions can happen at any time and there's always some risk when updating. In fact, not so long ago, one of those regressions occurred for me during an upgrade and broke the same application (Netilla). I was not happy about that either, but I believe that it was an accidental regression. It was fixed a few days later.
In this case, the regression was well known (by the package maintainers) in advance, and in fact, the entire reason for the update was to effect a regression! That's what makes this case different and worth discussing.
As to the possibility of restoring previous versions of packages, I believe it would be a welcome step forward if the user could just retrieve and reinstall the exact previous version of the packages he just updated, in the case of a detected regression. That still seems doable in the vast majority of cases. I do understand that in some exceptional cases the changes wrought by a newer package could be so far reaching as to make recovery by reinstallation of the older package unworkable.
I'll have to look into using LVM as a checkpoint mechanism to be able to revert failed updates. But if it can't be scripted up pretty easily, it won't be worth it.