If you haven’t already done so, you might want to price one before you go too much further, they’re pretty expensive. Brownells sells them.
They do a decent job of removing oil, loose debris and such. But, as noted above, you’ll probably still find some caked on carbon here and there that needs to manually removed.
They’re nice, but unless you’re going to be using one quite a bit, they aren’t – IMHO – worth the initial cost and the aggravation of maintaining.
If you decide to get one, be sure and use a liquid cleaner suitable for firearms. I’ve heard that the ammoniated cleaners commonly supplied with these can damage the epoxy that holds night sights in.
Personally, I’d rather just use brake cleaner.
(I just got some Slip 2000 Carbon Cutter mentioned by [b]shineit[/b] above, but really haven’t used it much thus far. It’s essentially a dunk and actually looks like it [b]might[/b] work as well as an ultrasonic cleaner setup - or maybe even better- for a lot less money.)