I recently switched my IM client from Trillian Pro to Pidgin, née GAIM. Trillian hasn't had an update in years, the Jabber support is bad, and it was acting wonky. Time to switch to an open source alternative.
Be careful what you wish for. Pidgin is amazing in a lot of ways; it supports a lot of protocols, has simple plugins, a solid communications library, etc. But it also has the breathtaking hostility to usability of so many open source apps. A lot of the GUI details aren't quite right and the docs are downright arrogant.
To be fair, Pidgin mostly works fine out of the box. Except the font is too small. No big deal, every app lets you configure the font, right? Ha! Just try the documented solution. Apparently I'm supposed to learn about GTK, and themes, and figure out where GTK places config files in Windows, then edit them with a text editor and insert 500 bytes of configuration directives for "imhtml-fix".
There's a proposal to add font controls in Pidgin, but the answer from the developer is "I think more people should know how to modify their system configuration settings". Because you know, chatting with your friends without squinting should require you spend hours researching some GUI toolkit no other app on your system uses.
Update: I stumbled across the Pidgin Extended Preferences Plugin. The page is incredibly coy; no download link (it's here) and no description of what the plugin actually does other than a grudging "additional preferences that have been commonly called for in the past from Pidgin". Which is why it doesn't show up on a search for pidgin font size. But if you click through the tiny screenshot you'll see there's a configuration option for font sizes! It even works! Well, once you figure out how to make a directory and copy a DLL over manually.
PS: the default font size is 8 point. Damn kids.