I never really thought I would be a fan of primes, but I bought the Thrifty Fifty (Canon 50mm f1.8) to try out and I'm pretty impressed. The large aperature gives the option to use a nice shallow DOF, which I really like for most sports.
The 50mm f1.8 lens isn't a fast focusing lens, but as long as you prefocus so the lens is close it is capable for sporting events. I think I will look into the 85mm lens that has the USM on it hoping that it will be faster to focus.
Anyway, I wanted to give a thumbs up to my first step to primes and let those who were thinking about primes know my first experience.
Here's a couple of pics that I grabbed last weekend with the super cheap 50mm lens.