I used to never ever report people, but once I started seeing the actions of the mods, the way the community was degenerating and quality posters leaving the site, I started doing it. But I only do it when a clear rule of the site has been broken or when I someone doing something that someone else got banned for.
For the record, though, even when I've cited the actual rule that being broken, I don't think any of my reports have led to moderation. There's a recent, clear troll thread that was made and absolutely nothing has happened. I really don't know what the problem is with the reporting process, but it's becoming clear to me it doesn't work the way it should.