They have them in DD2's school which is a new build. The teachers also use them (though I think the Head has his own).
The doors and walls are floor to ceiling so there is no likelihood that someone will hear the clank of the sanitary bin or unwrapping of sanitary products.
There are no mirrors either, but the students are not allowed makeup. If girls need to adjust their headscarves etc, their friends help them.
The whole school has been designed with glass walls etc so there aren't places to hide and I believe this does reduced bullying.
A girl was sexually assaulted in the toilets at a local school (not sure if it was my DD's) a few years back, so I think that overall they are a good idea.