I'm actually stunned. I expected it to be a bit sharper but maybe AFMA was not calibrated prior to testing. I compared these shots to some of mine recently taken with the 300 2.8L and 2XIII and I think mine are actually a bit sharper than these.
I'll wait for more samples to show up before I cast total judgement on the new lens.
Actually, you are right on. These images are a little soft. I have an old 600mm NON-IS lens that is 15 years old and the images are tack sharp. Not quite as sharp as my 300 f2.8 but very very sharp. The images presented in this "first impressions write-up" are a little soft. The first one is quite sharp but the following two are not. (even the heavily cropped indigo bunting should be much sharper even without any post processing)
I suspect that this lens was not MA calibrated on the camera body. Even being off by a few MA points will degrade the image dramatically especially when you are shooting with such a long focal length at subjects as close as this. The depth of field is so small that there is not any forgiveness if your focus misses just a tiny bit.
I'd be interested to know if Ethan adjusted the MA on this and if so what his method of determining the correct setting. This lens should be performing better then presented.