Well, I didn't get to attend any of the previews until today's soft opening. For the record, the park opened at 8am, and The Walking Dead opened at 9am. Went in immediately, and I'd say it has essentially no line at all until about 10:30. Then it began to get long fast.
Left the park at 11am, and saw that the line to get in to the park through bag check was literally snaking all the way through CityWalk, including wrapping around Hard Rock and coming back towards Yogurtland! Fortunately, they had it moving pretty fast. As far as I could see, every bag check station was open, and the were even adding four additional ones off to the side. Crazy!
Plus, we noticed they had the timed ticket Harry Potter entry machines all set up, as well as a queue for them. Certainly seem prepared to use them. If anyone else is there later today, it'd be interesting to see if they get used or not.