Riding fixed builds both strength and spin: you're seldom in the "perfect" gear so you have to develop a broader efficient power range. From that point of view it's great training. The reliability thing we've covered: less to break, less to maintain - thats why a fixie was the traditional winter training iron of roadies.

I just think it feels really nice. Which is kinda a Zen perv thing. In town, you spend a lot of time magic-coasting: almost zero effort, but your legs are moving. And you're in and out of the saddle, accelerating and braking - oh yeah, fixie braking with your legs is unique.

Just try it