I've bought the 70-300L on a special occasion with 200 euro discount, very close to 1000 euro, a price of which I feel is right for the lens. It is the first superzoom I own, my father has a 70-200L without IS. The 200 euro discount was a safety net for me, when I would not use the lens that much, I could sell it for about 1000euros and have a limited loss. Am I gonna sell it? No! I like it a lot. I can now make the shots I previously missed (in the zoo, streetphotos, from my kids off guard, etc) I feel 200mm would be too short for most of them. As the previous poster I will exchange it for a 70-200L 2.8IS MkII for free
. I like the size and the weight of it, I can easily carry it for a day in the zoo. I like the reach, I like the sharpness. However I also understand now why people want fast zooms. Backgrounds are nicely blurred, when there is enough space between the background and the subject, but could be better.
As with all lenses, it is a compromise between weight, range, light sensitivity and picture quality and it is a very good compromise. Could it have been better, yes. A 70-300L 2.8 IS for the same price and with the same weight would be nice.
A friend of me borrowed it for a day comparing it to his 70-200L IS F4 lens and he liked my a lot. The best picture of his 70-200L was marginally better than the best pic of my 70-300L, furthermore the 70-300L produced pictures that were comparable or slightly better than his 70-200LIS F4. Basicly it is a draw, you cannot go wrong with either of the two lenses. Do you need the extra reach of the 300L or do you need the F4 capability of the 70-200L and do you have the extra money for the 300?