I guess ideal pool temp is what you get used to! Here in Eastern Canada, with my propane heater and solar blanket, I keep it at 77 this time of year, which we find quite nice! In mid-summer, with no need for the heater, it can get up to 84, which I find too warm. When that happens, we keep the solar cover off overnight and let it cool down! My ideal temp is 80 (27 Celsius)- which southerners would find to be too cold. We keep the pool at swimming temperature from June 1st (sometimes earlier if the weather cooperates) through mid-September (and possibly the occasional weekend after that), so we get about 3 1/2 months of swimming, which is well worth the effort, in my opinion. Propane bills run about $600, about half of it during the initial 'burn'. We consider this to be a reasonable price for a summer's worth of entertainment. Have considered solar, but all that extra plumbing to fix just isn't worth it for me.
Northern pool survival tips: In addition to bleach for sanitation, I use a non-chlorinated shock (potassium monopersulfate) to eliminate down-time during our short season, so that the pool is always swimmable - the level of chlorine stays constant and there is no waiting for it to come down from shock level. It costs a bit more (I use one or two $60 tubs a season, shocking bi-weekly in the off-season, and weekly in mid-summer), but it maximizes the use of the pool, the water always sparkles, and the money saved by using BBB means I am still way ahead of what others pay for chemicals at the pool store.
A solar blanket is essential here, and stays on whenever the pool is not is use, unless it is sunny and there is no wind.
MaMa's going swimmin tomorrow! 
