I'm going through my first "winter" (as much as we have in Houston) with my new pool. It's a freeform shape with a waterfall and a round raised hot tub on one end. (see the link in my signature for pictures).
I've got a 400kBtu heater for the spa and I used it once earlier in the fall to heat up the pool to a comfortable temperature - though that was only about a 10 degree lift. I don't expect to heat the pool often, but when I do, I'd like to get the best use of the heat that I'm putting in.
I know very little about covers. I'd be interested is putting something on during the heating up process that would reduce heat loss/evaporation to the atmosphere before we're ready to use the pool.
I could see building a skeleton frame of PVC pipe to span across sections of the pool and covering it with a tarps, but I'm curious of there's a better way to approach it.