I visited the 'New' London Dungeons on the Saturday of South meet (rather than Chessington), and have mixed feelings about the place.
I arrived around 10:50, and the exterior queue was empty, as was inside - we walked straight in, had our bags checked by security, and then proceeded through to the dark corridor where you wait in line for roughly five minutes, in near pitch black darkness, to pay.
Something to note - This was happening in the old dungeons too, but they try to upsell you many different books etc when purchasing your ticket. Ever the money-grabbers..
Whilst I did enjoy myself, I also found myself wishing I was in the previous dungeons. At present, County Hall is just too clean, too polished, and not nearly as aged as it should be for the overall theme it's going for. After all, we are supposed to be exploring London in it's grimiest days. When you get in the pub, you'll see what I mean!
A few hidden surprises that I quite liked, that were unexpected!
The water ride was amusing, as was Drop Dead, of which I rode twice in quick succession (even with a group behind me!).
All in all, it has to age and settle in. At present, it's too clean, and even smells fresh. I am sure when it's bedded in it will come into it's own.