At $30 it's not cheap, most apps of this sort go for $10 to $20. On the other hand, it's not like there's much competition, and it's not like Spotlight is getting much better.
It's crazy, for example, that Spotlight doesn't have a "path" column (folder names). HoudahSpot does. HoudahSpot also plays nice with LaunchBar and PathFinder. On the other hand, HoudahSpot's Help file is pretty crummy.
I've started a two week trial. I'll update this post if I buy the app.