I was at a Tamron "Tailgate Tour" (
http://www.tamron-usa.com/tailgate/?...FQcpaQod7TQAjg ) last Friday at a local camera store and they had the 150-600mm, lens mounted on a tripod and focused on a sign across the street. I could not read the sign with my bare eyes but could easily read it through that lens. It was quite impressive...
No, I did not purchase one (although I was tempted). Instead, I ate some of their free hot dogs and purchased a new photo vest (not Tamron) to replace my old ragged vest!
One thing that I have noticed when using very long focal length lenses, often it is not the lens but the air clarity over great distances that results in less than optimally sharp images.
Your images, however. look quite good...
Congrats and have fun with the new glass...