I used Pidgin for a long time, then formatted and installed Windows 7, then decided to use Digsby.
Digsby is okay, the installation process sucks, it trys to get you to install all these tool bars and other crap software, just make sure to push decline.
It also uses your processor when you are idle to crunch numbers for some institute/program kind of like folding@home.
I would stick to Pidgin, it works fine and it doesn't do all this stupid shit that Digsby does.