They are great for very particular scenes, I'm a big fan-- I have 5 in My Dungeon.

A full size steel cage that a person can comfortably stand and sleep in, (and actually I can get in and out as well through the bars).

A long, padded full length horizontal one for laying down all the way, coffin-style (wood, leather and steel bars)

A semi-padded crate sized cage, (wood leather and steel bars) that someone can be on all fours in

A steel corner cage that someone stands in, nice and snug!

And a completely steel square cage with a neck-hole, so someone can be on all fours and have their head trapped but sticking out

I use them somewhat infrequently, when I do its more for elaborate scenes and longer sessions. Basically if I get to use a cage in a session, its a usually a really good one!

Used the crate shaped one today for My puppy.