I do not have one, but have been eyeing them for my new setup and thus, absorbing anything others have mentioned. One thing which was mentioned by a guy who recently purchased one is that storing salt water made with Reef Crystals for an extended period of time caused it to sludge up. He was actively searching for a new salt and SeaChem Salinity was suggested. I just read an article on Reef2Reef today about an AWC done through peristaltic pumps which seems like a neat idea... if it could provide an AWC from a more remote location (e.g. from another room) it would be my design of choice... but not sure how far those pumps can push or pull. The guy at my LFS also talked of having multiple failures and returns of AutoAqua products, primarily the Nano, so I am questioning their dependability.