Cons: Its a process hog, it puts a ridiculous amount of holes in your firewall, and is stupidly linked to onboard computer time, rather than message sequence.
It's a very practical way to communicate with a whole faction. Much better than WLM for example.
But it lags. Laaaaaaaags.
And I have issues with sound : FL sound being cut by the Skype alarm, and Skype sound continuing even after I cut my laptop's sound. I can say sound one more time if needed.
Its awful, crappy, clunky, annoying, hard to navigate and generally not user friendly.
Xfire, on the other hand
Tracks your no lifeishness - I've played nearly a year straight of games since 2007 =P
Easy group/chat room feature which allows the same thing as skype - to make permanent conversation rooms with members
However it lags, needlessly eats up your cpu cycles, isn't really encrypted, lags, has pop ups, doesn't support tabbed chat windows, uses a proprietary protocol that hasn't been reverse engineered (so no third party clients) oh, and it lags.