One thing I noticed (I didn't hear complaints about it, but it kind irked me) was that last year, the back of the badges reminded attendees of the personal info that was contained in the barcode, but this year that wasn't true. I think it's important to remind people what person info they're giving away.
That said, I heard much of the "thank you" "this rocks" "this is the best conference ever" comments. Since I was introducing speakers, I heard it a lot from them, but I also had an attendee kindly insist on buying me a drink one night because I was staff, despite my protests. Every year I hear even more positive comments.