I have just received my new 70-200mm f/4L IS lens which is intended to replace my wonderful non-IS version of that lens. All I can say from preliminary testing is WOW!
The images are absolutely great. I have not tested this lens head-to-head against my 70-200mm f/4L Non-IS version but, the images are at least equal if not better. That is really saying something because I have always considered the 70-200mm f/4L as one of my sharpest lenses.
The main value of this lens, of course is in the wonderful IS system. Canon has achieved a winner in this system. I am getting older and to tell you the truth, I cannot hold a camera/lens as stable as I could ten or twenty years ago. However, right out of the box, this lens provided tack sharp images at 1/45 second using the lens at 200mm.
This would normally be called a two stop advantage (1/FL = 1/200 second, 1 stop advantage = 1/100 second, 2 stop advantage = 1/50 or 1/45 second). However, I would have to test my holding ability to see if I can actually hold a lens steady at 1/FL or if I need to use 1/2xFL. If so, that would be a three stop advantage for me. I did not try 1/25 or 1/30 second but, as I play with the lens, I will learn my limitations.
I see no negative points regarding this lens.
Some photographers say that it is too expensive. That's only because the non-IS version is comparatively inexpensive. This lens is in the price range of the 70-300mm DO IS lens and will give better images than that lens. I have a 1.4x TC so the 200mm side can be stretched to 280mm with a f/5.6 aperture. The street price has come down and you can get this lens at less than MSRP.
Some folks shy away from the "white" color as attracting too much attention. I use a screw in metal filter rather than the OEM filter and the lens is much less imposing in looks. Besides, I have always used prefessional cameras and I am used to people looking at my gear. They really used to look at the 4x5 press cameras I used.
Some folks say that the tripod ring should be included. Perhaps it should but, maybe a lot of folks will use this lens hand held taking advantage of the IS. That way, they don't have to pay the extra price that an included tripod ring would cost. By the way, I have a ring from my "old" non-IS model.
I also have some 67mm filters which fit on the new lens thereby saving some bucks.
The final gripe by some folks is that this is f/4 rather than f/2.8. What can I say? Stating that the 2-3 f/stop advantage it gives will nulify that shortcoming in many instances will automatically bring out the cry "YOU CAN'T STOP MOVING OBJECTS WITH IS".
I will grant that point but, you cannot stop moving objects with an f/2.8 lens (IS or non-IS) that you have left at home because it is too heavy. The f/4L (in either configuration) is half the weight of the f/2.8L. The size is also smaller making it a much more transportable piece of gear.
If you can afford it - BUY THE IS VERSION it is that much more versatile however, if bucks are short - the non-IS f/4L is still a great lens and will continue to provide outstanding imagery with great build.
I can see myself using this IS lens FAR more than I used the lens it is replacing. IT IS A WINNER!