Let me venture to say this, and it is not directed at ANYONE in particular.
After you have seen/heard a program for years, you come in EXPECTING something. When they don't deliver what you expect (regardless of if it was good or bad), you will have something to say.
Example: The first time I saw SU in person was in 1994 at Robertson Stadium. When they played, I was amazed at the type of sound they put out, and I will never forget it. I saw them several times over the next few years. Then I saw them in Rice Stadium in 97. It wasn't quite the same as when I saw them in 94. 98 didn't have quite the same effect as 97. 2000 didn't quite hit me like 98.
WHY???? Because nothing will compare to when you FIRST became a fan. You start looking for things that you EXPECT to be there, and get tunnel vision while looking for those things.
In 94, SU's trumpets were monsters. When I saw them in 97, I was LISTENING for the trumpets, cuz that's what I remembered. I ALMOST looked past the fact that the B-Tones were tight as hell....
Basically what I'm getting at here is that you have to try to look at every performance like it's your first time seeing them. When you EXPECT something before-hand, you miss what actually happens because you are so busy looking for something that's not there.