I've never liked the idea as it seems like a cafe but now my 8 month old has started to crawl he's into everything he shouldn't! I don't leave him alone unless it looks like he's engrossed in a toy (which doesn't happen often) but I might quickly nip to the loo or something and by the time I've popped back he's banged his head on a door or something else.
He has a jumperoo but doesn't like it anymore :(