I've been on parade taping day and it was so packed.
It wasn't just the Hub or Main Street, either, although those were the worst. There were just so many extra people in the park hoping to watch the parade during the day without having to buy a party ticket that the lines were outrageous for most of the big-name attractions.
Knowing what I know now, I wouldn't go to the MK on taping day unless I had no other choice or if I had somebody in my party that had never seen the parade and wouldn't get another chance.