Sorry, I meant completion. That's the one, thanks!
Is it any good? It looks good, but stuff sometimes disappoint.
If you like autocompletion then yes, it's very good. At one point I had issues with startup time that I was pretty sure had been caused by it, but it's highly likely it had more to do with Clang than YCM (I can't remember the outcome fully, since I ended up moving to Emacs shortly after).