My hubby and I just did the Donald Rumbelow JtR tour a couple of weeks ago. I knew almost nothing about JtR before the tour, and (this is going to sound a little sick and twisted) I was a little disappointed that it wasn't really that horrifying to me. My honest reaction was "5 victims, that's it?"
I know, I'm a sicko clearly desensitized to real tragedy by Hollywood movies.
IMHO, the tour was more interesting for pointing out the very real (and still very clearly demarcated) boundary between money London and poverty London. The tour was more of a brief little social history of the period told through the story of Jack the Ripper, which was interesting in and of itself.
If you're looking for a ghoulish, Halloween-y type scarefest, this doesn't really do it, but I was glad we did it and found it interesting in other ways.