I think the "Classic mode" is really the biggest, most game-changing thing here. There are a whole lot of people who hate GNOME Shell (I am not one of them. I'm not a fan either, but I don't think the shell is a step backwards) and are either staying on the outdated GNOME2 platform or hacking on top of GNOME3 to bring back GNOME2.
This, I think, is a great solution which acknowledges the desire/need, but addresses it in a way that embraces newer technologies ("classic mode" is built on GNOME3, in fact), rather than simply rolling back to older dated ones.
Kudos to the GNOME team for this and the entire release!