I did this on the first two Saturdays last year. The three early-opening house were the tent/dome houses in the Woody Woodpecker/ET/Barney area. I arrived and got in as soon as the passholder early entry opened. I did get to do two houses right away (the 3D house and the sunken Spanish ship house) and and one of the nights the Poe house right away (on the second Saturday, the Poe house wasn't ready right away). It worked very well and I got through the 3 houses with pretty much no line or just a very small wait (5-10 minutes). The only problem was that since doing the 3 houses didn't take too long, I had to wait around for the rest of the house to open at the regular opening time for HHN...they even had a rope up just past the Men In Black area and would not let you in to other parts of the park until HHN opened for the rest of the people...so there was little to do unless you wanted to go through the houses again. There were also no scare-actors out yet.
They also were not honoring any express pass features until regular HHN opening time (but the lines were pretty short during the early entry time that you didn't really need to use the express pass).
Hope this helps.
