After reading mixed reviews of similar products I was skeptical, but nevertheless gave this one a shot.
I'm getting superb results cleaning eyeglasses by using lukewarm water mixed with a bit of dishsoap, and leaving them in for the full 8 minute cycle (which is the MGUC500's maximum setting). It does a particularly good job of eliminating the green gunk that collects behind the nose pads.
The shorter settings are useless, so I recommend this product over cheaper ones that only run for 3 minutes (unless you're willing to keep hitting the button, which I imagine would get old fast). I also tried just using plain tapwater, and even filtered water, but neither worked. Ignore the advertising saying it does. There are solvents you can buy specifically for ultrasonic, but I haven't tried any. According to Wikipedia's entry for Ultrasonic Cleaning, "use of a solvent appropriate for the item to be cleaned and the soiling enhances the effect. Cleaning normally lasts between three and six minutes."
The ritual is a bit involved: Add soap, fill tank, insert glasses (oriented so glass doesn't touch the bottom or sides of tank/tray), run for 480 seconds, remove glasses and rinse, pat dry (with microfiber cloth, or a paper towel if you're lazy and less paranoid about scratching). Empty tank, rinse and wipe dry. Often I let it run while I'm showering. Although they come out of the machine sparkling clean, for some reason I end up with spots if I let my glasses air-dry instead of patting them dry. If you want to get really fancy, I imagine blow-drying with cold air would work too.
Not exactly convenient, but the results are great.