Hipchat isn't bad but I vastly prefer IRC, particularly with a good IRC bot.
It's actually pretty neat, you can try it out on : https://jabbr.net (+ it's opensource if you want to implement your own team chat )
That's HipChat 2.1.1013 running on x64 in Vmware 10.0.2 w/ 8gb of a total of 32gb allocated. Oh yea, I'm doing nothing in HipChat, just idling in a single channel, with two inactive conversations with AFK people open. The chat window contains no animated GIFs or Youtube vids or anything wild either.
I've been strongly considering switching to using a regular XMPP client especially since feature creep seems to be be bringing features I don't want (video chat etc)
Edit: I should add the view is filtered, the CPU load + memory usage in the top is from an encrypted filesystem backup currently running