Seems like, depending on the time of year you go, most people who request a standard are upgraded to pool or Savannah room if AKLhas them available. Pool view is nice and Savannah view is great (have stayed in both). One thing you can do is fax in a request, or call the hotel directly and request a Savannah view room about four or five days before check-in.
If you are uncomfortable with this, you can always ask if one is available at check-in. The worst that would happen is that you would be offered the upgrade at a very nominal charge. Again, this is dependent on demand. Don't expect a free upgrade the week of Christmas, New Year's eve or Easter.
I think so many people get upgraded for free is because approximately 90% of the rooms are Savannah view. More people go for the lessor rate than there are rooms available at that rate. When you reserve a standard view, you are garanteed at least a standard view. If you reserve a Savannah view, you are paying extra to be garanteed at least a Savannah view.
Often I have read that Savannah views have been upgraded to Deluxe rooms and Deluxe rooms have been upgraded to Concierge. I think AKL tries to give you the best room available at check-in.
We have reserved standard view and been upgraded to pool view Christmas week and paid extra for Savannah view at Easter to make sure we got one. If your heart is set on Savannah view during a peak time, go ahead and reserve one when making reservations, that way you will be sure you get one and won't have to wonder if you will actually get one. Just remember, there aren't a large number of bunk bed rooms on the Savannahs. Seems more of them are pool view.