All of what
@Tuvalu said. All is spot on and exactly how we have experienced it. We did have one time where Main Street opened up at about 7:45am for an 8am EMH, but that was the exception not the rule and I think it was because it was a holiday and the turnstiles were getting a bit insane (shops weren't open yet, just the actual street).
My family would definitely prefer to sleep in, but the magic that we have experienced when we have gotten there very early is totally irreplaceable (picked as family of the day at both MK once and AK once, Epcot had a surprise early opening once - Soarin' with not a single other person in the theatre was amazing, Studios open early a couple times).