When I upgraded my Ubuntu machines from Feisty Fawn to Gutsy Gibbon the cool beryl/compiz desktop effects stopped being so cool. I have learned how to fix it, however, from a few awesome blog entries. Here's how I did it.
First, remove any oddball compiz/berylemerald repositories from your sources.list. Everything you need is in the standard Ubuntu Gutsy Gibbon repositories.
Next, remove any compiz/beryl packages that you previously had installed:
sudo apt-get remove compiz* && sudo apt-get autoremove sudo apt-get remove beryl* emerald* && sudo apt-get autoremove
Now, install the needful compiz packages:
sudo aptitude install compiz compizconfig-settings-manager
Now you can turn it on by running System->Preferences->Appearance and the clicking over to the Visual Effects tab. Choose Custom and then click on Preferences to bring up the settings manager. Then you can follow the How to set up Compiz Fusion instructions to get wobbly windows, desktop cube, and all the other good stuff set up.