Sharpness is a very personal and subjective thing. Every photographer has their own level of aceptable sharpness. Some are easily swayed by forums and other photographers, but cost has a lot to do with this. We all set our bar based on what we can afford and to be honest this is an irrational behaviour. Surely our view of aceptable sharpness should be defined by how large we print and that it looks like on the wall?
Here's a shot I took a few weeks ago of a Puffin. At the time, sharpness was the least of my concearns. At the time, composition, tripod craft, exposue and not scaring this chap off were my priority. I was using a 400mm f2.8 at the time and I didn't want to get any closer, so I fitted a 2x converter and shot it nearly wide open. It was only when i got back to base I realised how sharp it was....stunningly so!
Here's the image, 5DIII 400mm f2.8 and a 2x TC f6.3, Manual Exposure, Gitzo Systematic tripod
Here's the 100%, it's looking like a Flickr is aplying some jpeg compression to my image. It looks sharper on my local file.