I have the Sigma 24-70mm, and use it on my 20D it did not have to be re-chipped? and as far as the lack of HSM, it still focuses pretty quick. I use it all the time for indoor sports, gymnastics, volleyball, indoor soccer with great results.
I am really glad to hear about your good results with the Sigma 24-70. If my testing with the EF-S 17-85 IS shows that what I really need is a zoom, I will probably look to the Sigma 24-70. -kabl