A while back(which is the fork of the widely used Gnome 2 desktop), on Fedora 17.
It worked, but it had a couple of minor flaws, and I ended up going with Gnome 3 and tweaking it to get it like Gnome 2. It took some work, and it's not perfect — for example, there are minor font issues where text doesn't quite fit exactly in some window areas. Regardless, the issues are minor enough that they are hardly noticeable.
Recently, it was announced that Gnome 3.8, the latest release, is dropping Fallback Mode. Many (including me) have been using Fallback Mode to make Gnome 3 look and feel like Gnome 2. Now this support is going to be cut off. I don't know of any distributions yet that are including Gnome 3.8, but eventually it will become commonplace.
It has also been announced that Gnome 3.8 will have extensions to return the Gnome 2 look and feel, but I'm not holding my breath at this point as it's clear that the development on Gnome 3 is focused on the new (and oversimplistic) interface. I've tried Gnome 3 a lot, but I can't get it to work as efficiently as the Gnome 2 interface, which to me can fit more on the screen at once and requires less clicking to move around and get things done.
It seems the user base has been heard, and MATE is now targeted for the final Fedora 18 release in January.
Since rolling out Gnome 3 by default for a few of the latest versions of Fedora, it seems that the user base has been heard, and MATE is now targeted for the final Fedora 18 release in January. On top of this, Cinnamon will also be included, for those that like this environment. This is great news, and shows that Fedora is committed to providing the best desktop experience it can.
Including MATE will allow users to retain the old Gnome 2 desktop environment, on the latest Fedora release with all of the new binaries. I don't know what the future of MATE holds for us, but I think the user base has put it in high enough demand, at least until Gnome 3 settles in with those of us who dislike its default interface.
I have been recommending to hold off on upgrading Fedora for friends and relatives since Gnome 3 became the default in Fedora 15. We still have many using Fedora 14, the last full version to support the Gnome 2 desktop. Fedora 14 still runs fine, but it's quickly becoming outdated. Fedora supports upgrading up to two versions at a time, so I may try to upgrade those to Fedora 16, then 18, and enable the MATE desktop environment.
The alternative is to back up the /home/user folders, install a clean version of Fedora 18, and then put the /home/user folders back in place. When logging in with the username that matches the /home/user folder, all current settings and files will be completely in place because of the simplistic way GNU/Linux handles user data. The MATE solution on Fedora 18 will give the users very little UI change compared to Gnome 2, yet provide all of the latest applications.
One thing that may be an issue is that any custom preferences for native Gnome applications, like the Nautilus file manager, may need to be reset. This is because MATE needs to name these applications differently because it's not really Gnome 2, but a fork of it. This should be a minor issue, and once set should stay set as long as MATE is around.
The Gnome 3 desktop was an issue for a while, but as of Fedora 18 it should no longer be an issue with the Fedora series of distributions.