I've used it.
It works pretty well, but it's definitely messy. You'll get extra greasy gross liquid on your chainstays, seatstays, and some other random places. Definitely preferential to do it outside.
That said, it works pretty well on the actual chain. You still need some sort of toothbrush type item to clean the crank and cassette, though, otherwise all the gunk you cleaned off the chain goes right back on it.