We've been over the 4th (and are going again this year) - we've never had a horrible time. I don't think they really decorate, but do have a great fireworks show at MK, and at Epcot. There's plenty of indoor type activity to do during the day if the heat is just too much. The crowds are big, but we really only notice it during the fireworks, and it does take longer to get out of the park at the end of the night. I'd say if you absolutely hate crowds and have no patience at all, it's not the time to go. However, if you're a happy go lucky person and don't mind taking things slow it's not so bad.