I shoot sports quite frequently with it. I love the 45-85, 150, the 200 and the 300. Once in awhile I drag the 400 along but have rarely actually used it. Even the 300 gets "noticed", if you what I mean and people tend to start backing away when I hook up the 400.
I usually have the 150 on the 645 and the 200 on the 645Nii. Long telephoto isn't really all that necessary for kids soccer and softball. Actually with soccer I frequently forgo the really long stuff and mount the 45-85 on the 645Nii. I get some decent goal action that way. Something almost scary about a herd of young boys headed your way, each trying to kick a soccer ball.
I also like the 45-85 for those bleacher shots as well. Sometimes there is more excitement to photograph in the bleachers than on the field.