Evaporation - BAD WORD!
I live in the country, no real water sources, trucking it in is expensive - one of the reasons the cover stays on - I keep my water in the pool.
The heat gain without a cover is actually higher even if you take evaporative cooling into account, I think it was proven umpteen times on the forum, but then you have to top it off with cold water, plus you went through all the daily troubles of rolling that thing up!
I'm a firm believer in keeping it simple - the less work my pool is the better, that's why Ben's 3 B's are perfect, I hardly had to do a thing to my pool last year except add bleach and toss teh barracuda in once a week and it was always sparkling!