In defense of Black Diamond Circuit approach shoes
Our initial impressions of these shoes were not very favourable. Especially using them to boulder in was unpleasant.
A busted toe nail appears
Toe nail injuries hurt, in case you didn't know. On our recent second Ardennes trip, we spent five long days climbing for 8 hours per day. Even though Arie's La Sportiva Kataki are well broken in, they still caused his toe nail to get all smushed.
The only shoe that was tolerable to climb in without too much pain were these Circuit approach shoes. And lo and behold: they performed very well on rock. Arie climbed up to 5C routes with them, with some short overhanging sections. All in all they were reasonably comfortable, even if they are far from precise.
The other advantage
The other upside was that they are very collapsible, so on a multi-pitch route with a topout you can just flatten them and pack them. We'd advise against carrying them near your sandwiches though — wearing them without socks makes them smell something awful.
Okay okay, so we jumped the gun a little. They're still absolute trash for bouldering. But we wouldn't hesitate to lead anything up to 5C in them, they are very grippy on actual rock.