"The all new Ubuntu Tweak 0.5.5 came with a lot of feature
updates and bug fixes. One of the striking new feature addition is
the inclusion of PPA Purge functionality.
"PPA Purge alone is a good enough reason to install Ubuntu Tweak
in my opinion. If you are an avid Ubuntu user, you must have been
obviously playing around different software PPAs available out
there. And some PPAs can mess up your software badly. I had a
really bad Banshee mess up once. With PPA Purge, users can easily
revert to the previous version of package if they don't like the
one they've just installed from the PPA."