Since "Early Entry" returned as "Extra Magic HOUR", I don't think I've ever read a post from someone claiming that the attractions began running prior to the 8am EMH time.  Under the "Early Entry" program, the opening hours were a bit more flexible, but that's long since gone.
That said, the parks should start letting people through the turnstiles prior to the actual park opening time.  For example, at MK they will let you enter the park and get as far as Main Street.  At 8am the ropes will drop and all EMH attractions will officially be open.  So, there is still some benefit to being at the gate 20-30 minutes prior to the official opening time.  If you arrive at 7:55, you're likely to be behind a pretty big crowd.