7 out of 10 points and recommendedSilent, Affordable, Good ReachRelatively slow aperture range, Loose zoom ring
There's more to a good picture than sharpness. Although I don't have any experience with other EF lenses in this range, for my own work I've found the EF 100-300mm f/4.5-5.6 USM to be totally sufficient.reviewed December 26th, 2008 (purchased for $75)
It's a long lens with a slow maximum aperture and no IS. Big deal! Bring a tripod. CA is well-controlled and distortion is non-existant. Out of the dozens of pictures I've taken with this lens wide open at 300mm, I haven't found any that lack the sharpness to be "usable". Critical focus at 300mm is much more important. Of course the proof is in the pudding, as they say:
The bottom line is: If you need to stop motion or shoot without a tripod, this lens probably isn't for you. If you can allow yourself to work within its limitations, I can think of few advantages the EF 300mm f/2.8 has that could justify the difference in price.