I know what you mean about ease of use!!! I was really intigued by the COBIA system when I first saw it a couple of years ago, but I have never seen anybody that bought one report how they like it, though. I hope that the Retro works well for you, please let us know how well you like it after you've used it for a while! Even though it isn't directly connected to the pump piping, the same chemical reactions will occur, and you should browse the pool school posts on balancing/buffering the water for use with Electronic Chlorine Generators, and maintaining the right FC/CYA ratio . Iv'e been very happy following the recommendations (I'd strongly suggest reading about advantages of adding borates!), and I now have a more Trouble Free Pool!
Good Luck, and Best Wishes!!!