I first ordered the Cat Genie 60 a couple of years ago, and loved it. The only problem was that it would get clogged every couple of months, which was a huge pain, but the 120 seems to have fixed that problem very nicely. I have 3 cats, and even though I would try to clean their litter as often as possible, there was still always a smell in the house which was rather embarrassing when visitors came over. The very first day I got it and hooked up the Cat Genie, people commented on the difference, saying my house didn't smell anymore!
My sister was highly impressed, so when I purchased the 120 I gave her my 60 to try out, and she has really liked it as well. At some point she also hopes to upgrade to the 120. I share some people's wish that supplies could be purchased in a store such as PetSmart, since I go there all the time anyway---this is a wonderful product!!