When you only have one gear, you become the transmission, just as in distance running. The result is a much more aggressive and physical riding style.
When the light turns green, I like having to stand out of saddle and pound until I gain momentum. When I ride up into the McDowell Mtns (kind of like CO foothills), it's time to HTFU and get over the hills.
In fact, when I have been riding my geared road bikes for a while and am starting to feel gear lazy, a couple of longish rides on the SS will set me straight. I can say that SS riding makes me a stronger geared rider.
+1
I've been commuting on the FG everyday and purposely taking the more hilly route just to push it. I have only had my FG conversion for a week and already the way I ride my road bike has changed. I'm not so quick to shift down on inclines anymore, I'm more eager to attack the hills, and coasting makes my legs feel weird.
Oddly I can now track stand on my road bike better than the fixed gear.