We've all been to professional events that fall short of our expectations.
I've found myself battling the urge to wriggle and yawn more times than I care to remember and then the feedback form comes round and I'm struggling to say something nice. Oh there's nothing worse than feeling you've wasted your precious time. A bad event reflects terribly on the organiser and everyone involved.
On the other hand, the impact a really good event can have is often far reaching. There's nothing better than realising the time has flown by and you've had a great time, achieved what you wanted to and more and are leaving an event brimful of ideas and enthusiasm and singing the praises of the people who just gave you a really worthwhile experience.