We have visited WDW during late June only once. This was from June 19-25, 2003. The parks and resorts were definitely more crowded than our previous late May/early June visits and slightly more crowded than our mid-March visits, which were pretty heavily crowded. As mentioned in another post, parks stay open later which helps spread the crowds out over the day. All days seemed manageable with respect to crowds in the parks, except for Tuesday, June 24; MK was extremely crowded that day.