It's just a ppa, I see no problem with that.But if you're worried about such things, there are other good DE's too, XFCE, LXDE, or even just a simple WM like openbox or ratpoison. So far as I'm concerned they're all better than Gnome Shell.
..Although in fairness, the new Gnome 3.8 classic mode is kinda neat. =x
