We were at MK Fri 03/22/2013, the estimated arrival day for the heaviest of the Spring Breakers. We had an early pre-open breakfast ressie at Crystal Palace, and were inside the park for rope drop. That seemed to give us an edge on getting pretty smoothly to all the E-ticket rides before about 11:00am-ish when the heaviest of the crowds started arriving. The rest of the day, and especially in areas where parades/shows que up, was "sardines in a can" packed with guests. We used the railroad to get around the park, because the forward progress walking was down to a shuffle, and our group of four kept getting forcibly separated by various combinations of strollers, double-strollers, scooters, school groups, etc. Thank goodness we did not have any small kids with us or it would have been very stressful keeping track of everyone. The crowd stayed shoulder to shoulder until around 6-7pm when the light rain came. By fireworks time, the park had thinned considerably, but was still "busy" until close. IMHO, if you are OK with being in a shopping mall at Christmas, stuck in a packed elevator, or at Times Square New Years Eve, then don't let a phase 3 Spring Break crowd stop you from the fun of MK. We had a blast and would do it again with an small group of older kids and/or adults. Do not waste your time or money if you have crowd issues, or get easily frustrated with waiting for things. There are much better times to go.