At first they seemed very nice and handy. I'd put Auralex Acoustics 2" Wedges 60x120 with them on a wall and they did great.
As I saw in their package I could use it for bass traps also. That, I thought, it would be great! So the next year I've bought bass traps for my studio, but it seems I had a lot of expectations. Not only, the bass traps had fallen, but advesive marks were on the wall and also some foam of the bass traps was off when I had to remove them completely.
So, they can't hold heavy stuff, they damaged the foams and definately I had to paint the wall.
Thankfully I've found a double sided multipurpose mounting tape in the construction store of my area that seems to do a better job and it's not leaving marks on the walls at all. Beside that is more friendly with the foam absorbers.