I used the Canon 70-200 f4 before investing in the 70-200 f4IS and found both produce excellent results. It can be a little short on focal length for flying shots and the 1.4 converter helps. The converter is left on pretty much permanantly, with no need to stop down to counter any fall off of the image.
The image stabilisation is great for static shots.
It is probably the best lens I have owned and relatively easy for an "old un" like me to lug around all day.
Edit. I would add that the none IS 70-200 f4 was excellent too. Just that as one gets older the IS helps.