I'd say it's an asset that can quickly turn into a liability. As you mentioned, the main thing is to consider the ongoing upkeep costs, whether it's your own time or you're paying someone else to take care of it. I must say though, it is awful darn nice to be able to go for a dip on a hot day, preferably with a beer in hand. Makes life a little nicer and you'll probably find some new friends when people know you have a pool.