Would this lens have too slow of an AF system for sports? I have the Canon 70-200 f/4 right now and looking to go to f/2.8. I do sports weekly and would hate to invest in this lens if it won't do the job.
It's no speed demon, it's virtues are size & weight and the rather good optics.
Look at the Sigma 70-200 HSM as an alternative, all but the first version are nice & speedy. Another option is of course the Canon 70-200/2.8 USM non-IS.
The new Tamron with stabilization and ultrasonic motor is out; THAT will be your ticket, not the old one (which was reviewed at DPReview years ago and the author found the AF to be pretty horrible). http://www.dpreview.com/lensreviews/tamron_70-200_2p8_c16/
