riding a single speed is (should be) fun. like riding any other bike it should make you smile,brighten your day, enhance your fitness (anything is better than sitting on your bum doing nowt)and improve your skills/flow.
It certainly makes my local riding more fun than booting around on one of my other bikes with gears and suspension. (Those are for big days out)
unfortunately it does get rather cliquey and hi-jaked by abject cockendishness at times by the "look at me, look at me, my bike is so special it's the cycling equivalent of joey deacon"
all the "aren't we wacky brigade" can detract from what is for me, another great way to enjoy the trails.