Exactly what Overread says, you actually can't or shouldn't compare a 100% crop from a 7D with a 40D. A 100% crop on the 7D is way more magnified.
If you still want to compare you should view the 10MP photo on 100% and the 18MP on 55%.
@Gabebalasz: Wow, very impressive! Thanks for posting!
I didn't expect this sharpness with a 2x extender at all, I'm amazed.
Great job on your photos by the way, they are beautiful!
I think I was able to provide a decent demonstration of what the 120-300 OS and Canon III 2x TC is capable of.
While my BIF images on top of the previous page are no doubt less than impressive, those were shot under less than ideal conditions, plus we all know that a 2x TC is not a champ when it comes to AF tracking. I am personally OK with my 2x TC BIF shots, I had expected worse actually.
The latest static bird shots came out nice indeed, I am very happy with them. Conditions were nice yesterday and it showed. If these latest pictures had come out bad, than I would know by now that I have a problem
But I did expect good results from the sunny static shots since all my test shots indoors (with external flashes) had been quite sharp for 600mm.