After reading a number of negative comments (some scathing) about the Canon 75-300 EF 4-5.6 IS lens, which is one of the lenses I bought with my Canon EOS 20D and thought it to be a decent lens, I did several test shots with it and found it to certainly be good enough for my purposes. No doubt 'L' glass can do better since it is usually faster and uses better glass (I'm told), but Canon's 'L' lenses are also considerably more expensive, have less zoom range, and are bigger and heavier, the last two characteristics being critical factors to me since at my age with a bad back I prefer smaller and lighter for carrying around out in the field.

The heron shot below was taken with wide open aperture, one of any lens's worst settings for image quality, and at full zoom (300mm), one of this particular lens's worst settings for image quality. The moon was basically a snapshot taken while walking on a beach one evening and I was curious to see what I'd get.

I would be one of the last people to say the Canon 75-300 EF 4-5.6 IS lens is of professional quality, but I'd be one of the first to say it is a very good lens and well worth the money for those, like myself, that find image stabilization to be important. I have found the lens to be an excellent companion to the 17-85 EF-S 4-5.6 IS kit lens that came with my 20D, both lenses yielding images of comparable quality, image stabilized, and covering a range of 17-300mm (27-480mm in film terms) with only two lenses for a fairly impressive zoom range of 17.6X at a total cost of USD$900.