It's not that black and white. Yes, usability tends to carry with it some measure of sacrifice in security, but Skype used to have a lot more security, and was as easy to use as it is today. They're not absolutes. You can have "quite usable and very secure" and "very usable and quite secure", things none of the apps we're discussing are.

I don't have any big concerns with OTR (aside from the inability to do offline messaging,) just the implementions, mainly OTR in Adium. OTR in Pidgin appears to be decent, but hasn't received a lot of review, as far as I know, and Pidgin has its own problems/provides its own attack surface.