It's called weighing the pros and cons. Some newer versions of older programs are bloated with extra junk the user doesn't want nor need. Ex: adaware, azureus, windows vista. I regularly download adaware 6.1 over the newer version. It's smaller, sucks up less resources, and does what i want it to do.
Trillian 2.0 just also has a bitchen skin that hassen't been updated yet.