If you are considering this lens as an upgrade, do it sooner rather than later. If you are thinking that it's too expensive, and a lessser lens will work 'just as well' you are wrong.
This lens takes razor sharp pictures in every situation; Low light, sports, portraits, and anything else; I had been using the 75-300 IS F/4.5-5.6 Canon lens, but was having difficulty with school gyms and their low light; This lens blows it out of the water!
This lens is heavy; And expensive; But the quality is unmatched, and the images it produces are outstanding