I'll say this. Single speed does have its disadvantages, but for me, it makes me take better lines, and keep as much momentum as I can, which in turn makes me a better rider. When I would ride a mountain bike with gears I was more worried about what gear I needed to be in rather than taking good lines. Learning to take good lines on the single speed crosses over to a geared mountain bike, so it makes me faster overall. It's not for everyone but I like it.