I already posted some solutions to speed it up in the WP thread. Others started contributing too.
The whole thing needs to be completely rewritten. It's not just poorly implemented (slow, inefficient code), it's also poorly designed. The only good thing about it if you ask me is the fact that it keeps the content in the same place, i.e. does not create extra posts, or extra DB tables. But that also needs should be improved, and I posted about this aspect in these forums: viewtopic.php?f=4&t=4037
Yes, I know that people waited a few months until qTranslate was compatible with WP 3.5. Also, it seems the plugin author doesn't reply to anyone anymore ... I guess it's time to move on. I was careful enough not to have too much content in a 2nd language so it won't be so hard to switch. Slowness aside, it's reliability is questionable. For this kind of plugin I'm thinking of actually paying.
Until I switch, I've started writing my own piece of code (part of one of my Plugins) that is compatible with the qTranslate storage. Who knows, in time, I might completely replace qTranslate with it.