For muzzle devises and throwing something quickly in a vise, it works great plus you don't have to remove any optics. I've had trouble removing some very stubborn barrel nuts while using the BEV block though. I stick that upper in a regular upper vice block and I feel like I get a lot more leverage on it.
It works okay, but starting from scratch, I'd probably get a standard upper vice block.
That being said, their Armorer's Wrench is awesome