We were there last year during the taping. Even though the crowds were not insane like they are on a holiday weekend, the Saturday of the taping was the most crowded day at the MK of the whole week by far (however, I realize this could also have been to the fact that it was a Saturday....we were there Wednesday-Wednesday, so we only experieced one Saturday at the parks). There was a pretty big difference between that day and the rest of our vacation. However, we were only there from opening until early afternoon, so I can't speak for what the crowds were like the second part of the day. The thing that messed our day up was being routed behind the shops on Main Street. It was not a huge deal for my immediate family, but it was my grandmother's and cousin's first day ever at the MK, and their only day at the MK for that trip (they only joined us on our vacation for three days). They missed out on the experience of stepping onto Main Street and seeing the castle, which was so sad. And getting from point a to point b in the park was difficult....the hub and Main Street were pretty much blocked off the whole time during the hours we were there.
But with all that said, I'd take the parade taping day in the MK over a summer day or Holiday anytime!