Ok, with a Fresh Install of feisty, I have found many bugs in the default shipped Desktop Effects – the Compiz and you can find them here in the launchpad
And also I am not sure why Feisty is not having installed the Gnome Compiz Manager installed by default eventhough the compiz is installed by default.
To install gnome-compiz-manager in feisty, open your terminal and type
sudo apt-get install gnome-compiz-manager
Configuring compiz using this tool can make many of the bugs disappear. Most of the bugs appear becoz some of the settings are not set properly by the default compiz and this tool helps to. For example, for many, the Cube Workspae was disappearing and after once they configured it using the Gnome Compiz Manager , it works !