i can't speak to the non-IS version of the lens since i use the newer IS version. but i can tell u that i love shooting outdoor sports like baseball and soccer with 300mm lens. i highly recommend that u consider this focal length in a prime lens. i take a lot of tack sharp shots that continue to amaze me after many years of shooting with it as a professional. it is easily one of my favorite lenses. i sometimes use it with a 1.4x teleconverter to extend its range. this causes the lens to lose a stop to f/4, but no big deal. it still focuses really fast with the teleconverter and produces awesome images. i've never had an issue with my lens.
by the way, i never shoot with the IS turned on. i always shoot outdoor sports with the 300mm lens mounted on a monopod. in my opinion it is too heavy and awkward to shoot hand held. u should definitely get a monopod to use with this lens. u will love shooting this way and your image sharpness will be much better. plus, the lens and camera gets heavy after a while. this is not an issue if the lens if on a monopod.
Indeed, I do have a monopod already. I always use it with the 300mm F/4 just because I prefer to sit on my pelican case when I'm shooting sports. I've never had the luxury of owning a Canon lens with IS! haha
I do really like the 300mm focal length, but I find it quite short for most things. Thus involving a lot of cropping in post. The real aim would be to have a 400mm F/2.8 but that's just way out of reach at the moment! I would intend to buy a 1.4x teleconverter for use with the 300mm F/2.8 during the day, then use it without the converter for night games most of the time. I thought that was a reasonably good compromise for the price. Especially on the 1.3x cropped sensor of the 1D Mark IIN, or, I also have a 40D if I wanted a bit more reach but I've never been happy with the IQ from that camera.
I'm excited at the thoughts of getting my first big white! (well... it's bigger than some of the whites!)