BmB said:

And I certainly did not see a lousy screening, it was probably the best I possibly could have gone to.

Best you could have gone to still sounds kind of lousy if you saw softening around the edges. I was scrutinizing every inch of that screen the whole time, and the whole time I was amazed and how incredible sharp it was. Unless you just have super human visual perception, I think there is a very good chance your experience was compromised by equipment issues.

Zombie made a good point about most 70mms being blow ups. There hasn't really been a whole lot recorded on 70mm since the 60's, so unless you are watching mostly old films, the 70mm prints you've seen are likely 35mm blow ups anyway.