A few questions:
1) Is the noise in the sky from the camera or from recompression?
I'm referring to the "Anders Bergan" picture. The exif data is
missing on that picture.
2) How far were you from the subjects (gives me an idea of how the rig was to handle). Using a monopod or tripod?
Castledude - there shouldnt be _any_ visible digital noise at 100 ISO. Even at 800, you're hard pressed to notice it (depends on the image, to an extent). My guess is it's the jpeg compression making the pictures blocky.
Having tried to take similar pictures with a manual lens (600mm f8 CAT lens), I'd recommend _any_ autofocus.... tho the pro shooting next to me had the 600mm f4 on his 1Ds.....