I upgraded to 11.04 and discovered that my video card (a GeForce Go 7400) was blacklisted.
I can live without Unity but some of the other Compiz features, that I depend on, are also unavailable -- the most important being placing windows with the grid plugin, and the most satisfying being the cube rotation.
I have no idea why the former would be affected by my graphics card. I have tried forcing Unity (using the environment file) but it crashes as the Unity scholars promised. I have also switched to another driver (173, I believe) but that also has made no difference. Lastly, I reset Compiz back to its defaults. Nothing has worked. What else can I try? (Thanks.) (@Jorge: Thank you for the formatting assist.)
UPDATE: In searching for Compiz alternatives, I figured that I could set up Metacity to handle the window management. In so doing, I realized that Metacity had already become the default window manager, which explains why none of my Compiz settings are having any effect. The real problem, then, is that I can't run Compiz. Using "Compiz --replace" freezes the screen. Now that I have the equivalent of the grid functionality, I might stop while I'm ahead. Of course, that would be the first time I have ever stopped while I was ahead.