I UCed my 1st National this year as well, and my experience was very similar to yours. One really doesn't know the time involved prior to the tournament, along with the time involved during actual play. For 5 days I was on location from 1st pitch, to final pitch and had a great time (along with regular UC duties, my duties also included, line-up card approval, coin flips and assisting the UIC with evaluations.) The only negative was that the TD decided to follow 'code' and not compensate the UC.
But I would do it again as well.