I'd been wanting to stop-in here for a while but didn't have the opportunity to go until a couple of months ago. A friend and I took the one-hour tour during the day which we both thought was informative and interesting. I make my living connecting wires so I was Geeking-out over a lot of things we saw, my friend who was with me wouldn't know a 'Butt-Splice' from a 'Service Drop' but even she said she found it interesting. The guide we had seemed to have a lot of knowledge which was nice.
Only drawbacks are that there are very few (if any) places to sit-down at. Almost no shade, they won't let you walk around un-escorted, if you give them you E-mail address they will send you offers a lot (I'm not even sure what they are, I just delete them) and that it's in a really sketchy part of town.
They said they restore signs occasionally so I may stop back-in in another year or so and see what's changed.