They are absolutely wonderful for cleaning parts. I completely disassemble and clean everything I buy when I first get it, and my mech mods maybe once a week. Warm water, little squirt of dish soap, eight minute cycle, they come out spotless, even the threads. Works nicely on eyeglasses too, even gets the gunk out of the arm and nose pad hinges.
I use a Magnasonic MGUC500 I got from Amazon.ca for about $40 a while back, it hasn't failed me yet.
