Sigma 70-200/Canon 70-200 IS 2.8's for sport?

[CycleLife]

Do I really need to spen almost double just to get IS, my sports photography is mainly downhill MTB racing, where most of the time the light is poor. Any other solutions greatly appreciated.

[sirsloop]

Shutter speed is going to be king with sports photography. The more the better... unless you are doing panning shots with a racer (thats when IS is nice on a 200mm sports lens). I use the 70-200/2.8L without IS... no problems cause I'm always shooting 1/1000th of a second shutter. Need an even faster lens? Maybe an ef 135/2.0L?