I've used the 7720 on several of my past projects, a lot of times using it to crush the drum buss and blending that with a less crushed version. It came out pretty killer quite often. I've also done some experimenting with it on the master buss and crushed a mix upwards of 7-8 dB without much pumping going on. It was cool, but not quite the aesthetic I was going for and I lessened it.
Anywho, I've actually got mine for sale in the classifieds section. I'm asking $400 for it, which I think is a good deal. I mean, $550 for a new one is a good deal for what you get so $400 for a lightly used one should be a great deal. I'd keep it if I had some more audio work coming my way, but it's just sitting and someone really should put it to work.
Fun story: some jackhole emailed me through my craigslist ad and tried to lowball me by offering $250 for it. I'm not sure if I was more amused or insulted. It really didn't help that the dude came across as rude and condescending.