I almost started this exact same thread because a few of the people, friends and family, who have passed through the house over Christmas have complained that our house is "cool". They were all Texans so have no real idea what "cool" actually is.
We keep our house at 68° during the winter. If you're actively doing stuff and moving about, we feel that's a comfortable temperature. Now, I will admit that if you're just sitting around, doing nothing, watching TV, it can feel a little chilly but both my wife and I will wear a sweater or cardigan in that case and if I catch a nap in my chair I will use a fleece throw.
During the summer we keep the whole house at 76° mainly because it gets hot in the kitchen when my wife is working there. Me ... I'm usually outside all summer so 76° feels downright cold when I step inside.
I don't know what's happened to me. When I was a kid in Scotland, 68° was hot summer day, definitely T-shirt weather. My blood must be getting thinner as I get older.
What I can't understand is that we have friends who keep their house about 80° during the winter and at 70° during the summer. I would have thought that if 80° is a comfortable temperature during the winter, it would have been a comfortable temperature during the summer too .... and a darned sight cheaper.