After much deliberation and after some time with the older 75-300 and the 70-200mmL lens, I decided that the 70-300 IS lense was the right lens for my needs. Although not as sharp as the white L lenses this lens will not leave much to desire if your subject requires no cropping. If you are using this for portrait photography you will certainly not miss anything. Since this is a slow lens and likely you will be using it wide open I am only showing wide open test images.

My conclusions are that this lens is the one to get if you are not shooting indoor sports or if you want to lighten your load. I carry this on 40D and a 24-105 or 16-35 on my 5D.

For this test I am using a 5D at 800 iso and shooting at large JPG setting (stairstep)

This is 300mm at F5.6 use the rollover to see the center at 100%

I then moved closer to the wall and shot this at 200mm and the maximum aperture is now F5.0

Again a little Closer and this is 100mm at F4.5 still wide open.

Now the Corners

300mm 5.6

200mm 5.0

100mm 4.5

As you can see in the corner crops it is considerably softer. If you are using this lens on a crop camera you will get better results. You can also see noticable light falloff in the corners on the full frame images.

Please use my link if you plan on purchasing this lens.