We just got back from our first summer trip - the pools were too hot for our tastes! They felt like you were in a hot tub - not what you are looking for on a 90 degree humid afternoon! It was much more refreshing to take a cool shower in the A/C hotel room!
That said - we've always gone swimming during our winter trips, even though the weather has been pretty cool. My girls have been brought up in the White Mts so they are used to cold water. We found the resort pools to be heated to a comfy temp, but the lazy river at the water park was FRIGID! Couldn't do it! The wave pool and slides were also chilly - but nothing like the river!