The 70-300 IS USM is a great lens. Is it an "L" lens? No, but it doesn't have to be. I have done sharpness comparisons between the 70-200 f4L and the 70-300 IS USM at 200mm and they are both amazing. The 300 loses a little
detail but it is worth it for the extra reach. I will never sell mine. I still use it and will continue to do so. It is worth every penny spent. It's a great lens in the EF line-up.
Too many people out there think that unless the lens is white or comes with a "red stripe" it is not worth owning. I do not believe that. Canon has several non-"L" lenses out there that are fantastic and some are even EF-s, the HORROR!!!
Do yourself a favor, get some 1/16' tomato red 3m stripe and put a band over the gold stripe at the end of the lens. That way no one will complain or even care to comment...