Well, they're not for me, cuz I can't but I think they're a great idea!
As for the whatabouters..
Camera over the top - assuming someone has managed to get into a managed toilet area, evade the people managing it, and got out a phone, they'll be able to film a wobbly shot of the top of someones head, from that angle you'll see absolutely fuck all unless the person in there does a hand stand which, even at Glastonbury, I doubt they'll be doing.
No door - again, you have to go up a couple of steps and turn left to see anything, time enough to shout 'oi piss off' - its a managed area, these are designed for managed areas. It isn't going to happen except by accident in which case the accidental intruder will piss off before seeing a thing.
Can't squat, won't squat - fine, they're not for you, use of the options that is.
But for the people they ARE for.. they're great, they take the pressure off the other options, they involve less lorry trips, they're a great ADDITIONAL option and if I were able to use one, I would.