Just saw this photo gallery article on Yahoo! Homes where the #6 turnoff for home buyers is an above-ground pool and the #7 turnoff is an in-ground pool. They caveat that in-ground may be OK in areas where such pools are common such as in hot climates, but this article says that one of the main concerns is seeing a backyard pool as a huge maintenance issue. Of course, we know that it doesn't have to be that way.
In our neighborhood, around 60% of the homes have pools, mostly in-ground. Based on sales comps, it looks like the homes with pools are valued on average around $50,000 higher than those without. Obviously this will depend on the neighborhood, but that article is making a blanket statement that clearly is not true everywhere. We're in northern California and not in the hottest part (we're near the Bay) and while we have nice summers, it's not like southern California, Arizona, south Texas or south Florida.