Unity stamped over a bunch of my keyboard shortcuts, so I took the opportunity to learn xmonad (with gnome classic) and haven't looked back.
Lion actually improved that a lot: Fullscreen apps integrated with Spaces gives a large part of what I use X<onad for. If they'd combined that with Windows 7's snapping of windows to half-screen, that would cover 75% of my XMonad usage. It's really a shame that XMonad is Linux-only. (Or that Firefox users expect Windows&OSX ports, depending on your perspective).