This looks interesting. I don't think I can go though as it's on a 'working day' though I could always take a day off. I'll wait until closer to the date to decide as my schedule is getting filled up quickly with travel.
One concern I have with this type of tour is the 'gangbang' effect. The image from the link shows a lot of people in a pretty small space, so are people jostling for position like in a paparazzi scrum?