I did one at Colonial Williamsburgh with my family when I was in 6th grade. It was a lot of fun with just the right amount of creepiness. My mom is obsessed with paranormal stuff & it was interesting to see a completely different side of one of my favorite vacation spots. I would definitely go on another one.
I did one here in Kansas City called Ghosts and Gangsters and enjoyed it for the most part.Unfortunately many of the places on the tour are still operating private businesses or private residences so contact was often limited to the sidewalk or drive by stories.
I recently received a Groupon invite stating that the production company that stages the tours will also be doing a ghost hunting tour. That would be very cool if it is hands on experience.
The Pike Place Market here in Seattle has a ghost tour that is pretty popular, and supposedly good. But I haven't been on it yet. I have been on the Underground Tour a couple of times, and the tour guide makes all the difference.