Agree with all the people about a good lens, you need a lens with at least an f2.8 aperture and image stabilization for fast sports. The 6 frames per second of the 50D is adequate, just make sure you learn how to anticipate the action and pan.
this camera is GREAT for any and everything!! i've taken some great sports pictures with the lens it came with, but i'm sure it would be even better with a special lens. also, it really depends on the amount of light; if there's lots of light, no problem!! it's trickier the less light there is. the camera is amazing. i couldn't be happier with it in any way!! good luck!!