Until you try it, the reasons for SS/FG are not really comprehensable. Sure, it's less maintenence, more efficient (arguable), quieter (arguable), but the real reason is that its just more fun. There's just something visceral about getting there without having to shift gears. SS frees your mind up to enjoy things besides the bike.

I did a cheap SS conversion on my old mtn. bike last summer as well as build up a light, fast, expensive, carbon roadbike. If I had done the SS conversion first, there wouldn't be a roadbike in my stable. I put more miles on my SS over the last year than my other two bikes combined. That incudes recreation as well as commuting. The added bennefit in my case is that is has definately made me a better cyclist.