The current version works fine on OSX Snowleopard (10.6.5). Quicksilver used to be essential for me in using my Mac. Now it has become a reflex to invoke the QS bezel and launch apps or calculate numbers. But Quicksilver is less quick than it used to be. Sometimes when I launch multiple apps at once it misses an app or two. Everyday processes on my Mac can cause delay in responsiveness and I find myself often waiting for the bezel to appear after invoking it. There are many more things you can do with QS other than launching apps but you have to take the time to learn what it can do.

Overall it's a great launcher that stays out of the way until you need it. But if you aren't already dependent on it, I'd suggest skipping this app. Unless the code is updated and optimized to be more responsive, and now that it's open source and hasn't been updated since Nov. 2009 I don't see that happening, it's not worth using anymore.