Check out this link if your serious about cleaning your AR in a sonic cleaner.
It has to be expensive but it would be the only game in town that I have found.
I also use an untrasonic for all my cleaning needs, including my shower heads with CLR and anything else I can find to put in it.
I use mine exactly as Cryogenic419 does and for the same reasons.
I use Hornady's solution and also a Lemi-shine (from Wallmart, 3.99 a bottle) and a squirt of dawn dishwashing detergent. Works about as well as Hornady's One Shot for brass. You have to use a different solution for steel products, Hornady sells it also.
I've never cleaned a whole pistol in mine but I throw my 9mm pistol barrels in mine once in a while.
I've never used stainless steel pins and cleaning solution in my rotary tumbler so I can't comment on it. I'm sure it works very well also. Theres a lot of good feedback on the other forums about it.