If you give people something for no charge, they will always take advantage of it.....hence the huge wait times. When you had to pay $12 to stay in MK an extra 3 hours, there were only about 5,000 wrist bands printed. If there had been more people clamoring for more wrist bands, you can bet Disney would have made them up. So, now...we have extra hours for no charge, but huge lines. And of course people will shop/eat if the lines are too long. Disney wins. If you are riding BTMRR 5 times in a row, then hoofing it over to HM and riding that several times in a row and then over to Space Mt for a few more turns...well, obviously you are not shopping. You will most likely get your fill of riding the biggies and then go back to your resort, shoppingbag-less.
With the EMH Disney gets a slew more people in the parks (all of them vs just MK) and they spend much more than the previous $12 a head got them. Sure they have more overhead but they had that anyway with the pay extra hours.
So, I figure they will keep this system intact until Nov '06. Then maybe do a variation of it. Maybe pay for extra hours in all the parks. Sure hope so...I loved the E-nights.