I still use 10.04 as it is an LTS release, but I was thinking to upgrade to 12.04 when it gets released, because it will be an LTS as well, but I really hate Unity.
Never the less, you can switch desktop environments on Ubuntu like socks, unlike windows Explorer that you are stuck with it.
On Ubuntu you can choose from Unity, Gnome, KDE, AWM, X and many other, although I prefer Gnome over anything.