The S2 is an excellent "all purpose" camera, and that is what Canon designed it for. As a pure 'sports' camera, look to another model.
Sports are one thing that influenced me to select the s3 (mainly my son trying to get decent pictures at ballgames). Not the only consideration but a significant one. If you were getting a mid-price consumer camera like this only
for sports, which would you choose? (I can see what the pro's use at the games, and obviously I'm not trying to be in their league.)