This is really going to be 2 reviews - crop and full frame. But first a little bit of background: I started out my telephotos with the 55-250 IS. Did ok, but I wanted the 70-200 for it's sharpness and clarity. Moved up to the 70-200 f4L non IS. I was cheap and thought I could make it without the IS. Did this for a little while and then upgraded to the IS model.
Build quality is great, feels very solid and the zoom/focus rings have a nice smooth action. Like my 24-105L it feels solid without feeling heavy.
Sharpness is otherworldly for a zoom and colors/contrast are great.
On a crop, the range on this lens is excellent. When I had a 5D and a 7D, I paired the 24-105L with the 5D and 70-200 IS with the 7D. This made a very versatile combo for travel, motorsports, even weddings. Using the 7D AF system plus the fast focus USM, this was a crazy fast combo with excellent tracking abilities. Panning at 1/30s at 200mm (IS mode 2) was very possible and helped me crank out some good results. Some even down to 1/5 sec, but few keepers.
On my 5D, it has been more of a mixed bag. AF is a little slower, but still not slow by any means. AF accuracy is just as good. The range is just what trips me up. It seems to be not wide enough at the 70 end to be useful and keeps me wanting for range at the long end. Seems kind of in between to me. I have not enjoyed it as much as using my primes for portraits. Obviously this range is popular with portrait photographers (the 70-200 2.8 is the staple), but it just doesn't work for me.
It makes a good travel companion to the 24-105L and is light enough to bring with you without much of a thought. The fixed length can make it tricky to pack tho. I carry mine attached to camera in a Lowepro 100AW with the 24-105 in the top pocket. Lens hoods reversed on both.
Since I sold my 7D, I have rarely used this lens. It comes out when it is time to go on a trip or the occasional motorsports event, but it has not been earning it's keep for me lately. My thoughts are to sell for a 135L to give me another option for portraits and that trademark look.
All photos below are taken with my 5D and the 70-200 f4L IS:
IMAGE LINK: https://flic.kr/p/oZsKe2 Hillclimb favs (41) by Bridgesphoto, on Flickr