I've done the visit and it was extremely useful, but there's a limit to what you can learn in such a short time.
Watching the SBS screen while listening to the RT has been invaluable to me. Yes, 40% of the flights into a major airport don't appear on the screen. That might be a disappointment to an anorak, but to me it's actually a benefit! Working out where they are on the screen from the ATC instructions, and mentally interpolating them into the traffic flow, is an excellent way of developing a sound understanding of 3D airspace.
I assume your point about cock-ups was not serious since they will be picked up by more reliable means and by more important people than me.
Sal