Haven't used it but did use similar ones like it. It will depend on the type of GPU you have (does they run hot? reference/blower model? single fan? etc..) but generally when you have GPUs so close to each other, you install aux fans. So thats why there are holes on each row, for the fans.

But then additional fans mean more power consumed and less profit. Also, DIY rig racks/cases are always cheaper. You don't need fancy rig cases like this to mine.