The big sell with those in with the mobile pro crowd. They can load up a lot of gear into what would otherwise require a 10-space rack. So as they move from gig to gig, they can easily carry their favorite toys with them...but even the small/mid studios are into them I think mainly for the same "size" reason. Most are using DAWs, so their mix position footprint is a lot smaller, and with a couple of these 500 racks, they could have a tone of gear close to them.
I considered getting one just to load up with nothing but EQ modules...as that is where I feel my console is a bit lacking. It doesn't have really high-end EQ. So a 500 rack would give me roughly 10 channels (depends on the rack).
Of course...to get the 500 rack plus load it...I would be looking at 3500-4000 minimum...for 10 channels of EQ.
So I figured for $2-3k more, it would make more sense to just find a sweet used console and get 32 channels of great EQ, plus everything else that comes with it....and just upgrade my console instead of having one 500 rack.
Still looking....