I have one for my set up. I've had it for about two years now. Its biggest strength is that it wont add more than you program it add.
The biggest drawback is that it wont adapt to different evaporation rates. In winter, my tank evaporates more water than in summer...need to remember to change the settings winter/summer....
But because of that, I did not have a major meltdown when my skimmer went nuts and blew water all over the inside of my stand....
People who have had AT units plumbed directly to their sump have had wipeouts due to that exact thing. Skimmer goes nuts or a small leak develops somewhere and the AT unit keeps adding RO water, lowering salinity.
As it was I just had a messy stand to deal with.
Nick