SunHeater Solar Heating for Inground - feedback?

[Spensar]

I saw that the Sunheater solar heating kits are available for inground pools now. Maybe this is old stuff, but I had only seen them for above ground before. They are providing roof mount panels and connections for a 15x30 foot pool for $500 and claiming heating capability of 10 degrees F. That's pretty cheap, any feedback on these and how they work?

Can't swing it this year but that may be a good option to supplement by natural gas heater.

I saw the kit at Costco online - http://tinyurl.com/32hpya