I wouldn't rely on the guy at HD for knowledgeable input. Talk to your local pool suppliers and find out what type of heating works best in your area. I think your decision would be based on how warm you want to keep the water, the type weather you have and the expense to install the solar heater.

Solar pool heating is perhaps the best "solar thermal" application. I built many of them 30-35 yrs ago. Generally you want about 50% of the sq ft of the pools surface in unglazed solar collectors. This is just like any other mechanical system. Use quality components, install them properly and you have a nice cost effective system that will do what you want.

I won't say that there are no knowledgable people in HD, but I haven't found consistency of knowledge with them. Several years ago in my previous home area HD built a store and actively went out to all the plumbing & heating and electrical supply houses and hired some of their best people. They built the business with these folks and then in about 9 months laid them all off and hired new cheaper and less knowledgable people, and so it goes.

Update: I went to my local pool suply store and looked into ordering one from them. They told me they use to stock them years back but they stopped. apparently their company ordered 20 of them...19 of them were returned. They said they could order me one but after hearing that (and the fact that I cant find anyone to Iinstall it) im kind of giving up on it. :( I went with the solar rings.. im excited to see how well they work!