I debated on getting the 2.8 or the 4.0 version of the 70-200 mm lens for quite some time. I finally decided on the 70-200 mm f4 L IS USM lens for a variety of reasons. It's quite a bit more reasonable in price, it's lighter and if I am shooting indoor sports, I just raise the ISO and am still able to get good images. I recently shot for a magazine in Macau the Sampras/Agassi exhibition using the lens. For outdoor sports, it's more than fast enough for my needs.