A big +1 on oversizing the SWCG.

While it's true it won't save money, I find the convenience worth it (I do not enjoy pool maintenance).

Another important thing to keep in mind is to only use the SWCG to maintain chlorine level. Do not use it to raise CL or shock the pool. Using it only to maintain CL will greatly extend the life of the cell (I learned this the hard/expensive way).

It seems to be the consensus here that the Hayward and Autopilot units are the best. I have the Aqua Rite (now made by Hayward) rated for 40k gal (our pool is 20k gal) and would recommend it. It was installed in early 2004.