I basically hate every one of these services that I've ever used. Crashy, resource-intensive clients.

At work we use HipChat which is "better than skype", but still pretty crap. In stark contrast to the rest of the Atlassian suite which is basically good.

IRC, in the form of irssi+screen on some kind of unix host, is however awesome. There's no great mobile solution, and OTR crypto should be available on top.

What's amazing to me is so many companies in this space and so much money and all the products suck.