We were there this past July 4th! DH and I saw MK fireworks on the 3rd. They were great. On the 4th, we were in Epcot and actually got to see MGM's at 9 p.m. (they were "above" the American Pavillion and then we saw EPCOT's at 10. I think they were the best of all! Wonderful ending! We stayed at OKW and actually got to see Pleasure Island's from our balcony! MGM's and PI's were purely luck.
Epcot was very crowded! We got there after our 4:20 AR at Olivia's, so maybe around 6ish. We just did SE and U of E. Also the Norway boatride.
It was VERY hot--no breeze. We picked a spot and waited for a LONG time. Bring a small towel or something to sit on. Lightening started and I'm a wimp, so we ended up losing our spot and waiting in the outdoor eating area of Norway. Came out and joined the crowd when the fireworks started. Unfortunately, my view was obstructed.
The fireworks were worth it all, however! My kids were amazed (18, 16, 14, 11). We're not in a rush to go back in the summer heat, but the fireworks for the 4th were enough to bring me back again in the future.