I used the wedges to sound proof a pair of panel doors, and scattered the rest around my studio. When you have them lined up they look great and they really do the job cutting the noise down, and lowering the general brightness of a room.
I tore down all the carpet on my walls and got my studio re-plastered and painted blood red. It's looks awesome, but the room ringed like a call center, but the wedges have cut it down big time.
They fit great on the door and the few bits I had to trim were really easy to cut out.
I used a spray can of carpet glue. It bonded really well with the wedges and i haven't had any pealing.
The only things i'd say to watch out for is if you are using them on a panel your going to put a screw in afterwards, cut a hole the size of a pen in it first, because otherwise if you don't the screw treads will grab the foam, spin it, and you'll have a hole bigger than a two euro piece.
Also the wedges attract people that like to pick at things like bubble wrap attracts people that like to pop things. It's foam, not Kevlar, so keep the pickers away.