On the topic of useable image edges and corners, These three images were taken "fresh off the plane" on a trip to Tokyo last year. They were literally in the first two dozen frames I made wandering around the Tokyo station precinct. My settings needed a bit of work, the choice of shutter priority was not flawed as such, but familiarity with the camera was lacking.
The fear? An awareness of the supposedly weak corners and edges on the 17mm. To be avoided!
The Ignorance? Forgetting that and shooting in shutter priority, getting the above image nearly wide open.