It looks like the check-in procedures at 'Ohana have been changed, which could make it more difficult to walk-in without a reservation.
Under the old system, guests stood in the same line whether they had reservations or not. Typically, a non-reservation guest would still be able to get in the queue, obtain a pager, go sit-down and order drinks, and wait anywhere from a few minutes to a few hours for a table to open up (I've done this on many occasions).
The check-in podium has now been moved to the other side of the building, by Samoa Snacks. There are now two lines, one for guests with reservations and one for walk-ins. As it was explained to me, the priority now is to make sure that guests with reservations can be seated in a more timely fashion. If the restaurant is undersold for the evening (not usual), then guests waiting in the walk-in line will be seated to fill the openings. However, if the restaurant is booked for the evening, no guests in the walk-in line will be seated unless/until there is a no-show. A guest has 20 minutes past the reservation time to check-in before being classified as a no-show. Under the new system, guests waiting in the walk-in line could be there for some time, and not even get into the restaurant, depending on their position in the queue.
I noticed the family that was at the front of the walk-in line stood there for at least 90 minutes. I'm not sure if they ultimately were successful or, rather, grew tired of waiting in line. The unfortunate thing is that it appears guests in the walk-in line cannot obtain a pager and, therefore, must physically wait in the walk-in line for a dining spot to open up.
I have no idea how this will work in practice, especially depending on the time of year or what time guests usually dine. Perhaps late diners will have more/easier success. Determining which family member gets to wait in the walk-in line could also get interesting.