I have been using these in everyday life a quite a long time now. We have had these in several homes with different walls. I have mounted them to concrete and wood walls with no problem what so ever. Just be use You use right kind of screws and plugs especially in concrete wall.
These are made of plastic, but are solid and high quality. The mechanism is both secure and quite bullet proof. I have used these with both steel string and electric guitars and they have always worked fine.
It is really nice that they came white, too, if You have white walls.
Can't find any drawbacks - I highly recommend these!