ive had the original 70-200 for seven years. i recently purchased the IS II. i'd say the original is more than fine for nearly everyone - it is an amazing lens - very accurate and reliable. the af on the new lens is faster and more accurate in low light and i personally think the background blur is noticeably more pleasing and smooth.the IS II is also quite a bit heavier than the original. i've never minded a substantial feeling lens but this one is heavy.there is also an additional weather seal on the rear of the lens that touches the camera when mounted. this was actually one of my main reasons for updating.