On a fresh install of Ubuntu 11.10 I tried Unity for a couple of weeks, and then Gnome 3 for a few days. After that I installed xubuntu-desktop (which is XFCE) and am much happier with that.
Unity seems to be aimed at using less screen real estate (especially vertical). However, XFCE can quickly be configured to use one auto-hiding vertical panel which is ideal for a widescreen laptop or netbook.
One of my biggest beefs with Gnome is that I can't find a way to deactivate the raising of a window when I click in that window.