We had one in 4-H. Well, it's still there. The first one they put up wrong or did something and something happened to it so they had to replace it - but that's beside the point.
We loved it. We get A LOT of snow up here in the winter so it was awesome for winter riding. And in the summer it didn't get TOO hot. We had a huge one with garage-like doors on both ends so we'd open them and get a good breeze through. It sometimes was actually cooler in there because it was a light creamy color.
Expensive but very much worth it!
TM Tardy's Chick "Hunter" - 13 yo Paint
Remmy - 18 yo Morgan/QH cross
Gunner 3/31/11, Heidi 7/2009 Miniature Sicilian donkey