We visited during 4th of July a couple of years ago. Based on advice found on these boards, we went to MK on the 3rd for the fireworks and did Epcot on the 4th (we love Illuminations and we wanted a picture with the characters in their patriotic outfits). We heard rumors that MK closed to maybe Phase I early in the day on the 4th but were never able to confirm it. MK on the 3rd was very busy but manageable. We did stake out our spot probably 1.5-2 hours in advance for the fireworks but only because we wanted to be on Main Street near the castle so that we could see the perimeter fireworks better. This year may be different as the 4th falls on a Friday which could entice more local people to visit since it is a three day weekend.