There are quite a few episodes where nothing significant happens. However, there was an episode from the end of the 2nd season I believe, where they were in a lighthouse, and there were shadow-like figures on the camera. One of them appeard to be above them on the stairs...zoomed to the top, and peered over at them from above.
That was some of the most convincing evidence I've seen on any of the "Ghost Hunter" type shows. they've had other small spots of luck also...but you'd have to watch all the shows to be around to catch them.
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Part of the premise of Ghost Hunters, is that they approach everything from being skeptical, and try to find a reason for phenomenon and try to disprove what people say they are hearing and seeing when they investigate...over the course of the show though, they do experience things they can't explain, and classify as paranormal. But coming from that perspective, no, they don't catch a ton of evidence...but when they do, I usually feel it's pretty solid.