I use them a lot!
I live in an apartment and have to leave soon, so I was looking for a mobile acoustic treatment. These panels just got the job done. You can't make a perfect treatment with them, but still much much better than nothing!
Also I travel with them a lots, going to rehearshal rooms and recording live drums, guitars, vocals, etc. They're really a game changer for me, I can somewhat make an okay acoustics in rehearshal rooms.
Bought 6 pieces, using all of them all the time.
If you have somewhat the same circumstances than me, I highly recommend to get these!