I'm with Mike and Suz on this on. To not have to go back to your room, find your vest from under your bed, donn it and walk down the hall and stairs with 1000 other vested cruisers is a blessing.
I'm sure RC has answered all of the important questions before implementing this radical decision. According to Adam Goldstein, president of RC, all the ships in the fleet will eventually be fitted with this new idea as heard on his 09/02/2009 broadcast. And, as CruiseQueen states, you still go to the drill and "listen attentively" to all directions from the captain/crew.
Then, you can go on your merry way instead of trudging back two flights of stairs, down the hallway and into your room.