One more question:
If the times change from the time you select to the time you book to the time you confirm, how do you know when to actually select the ride? I'm afraid if I wait until the time I need, it will be much later than the time I really want.
This won't be an issue for most attractions. The time you end up with won't be much different (if any) from the time you select.
But for the handful of high-demand items, it can be tricky. If you are not in the 7:00 to 7:15 am time period, you will see a time on the Tip Board (Time 1). If you click it and then see a time which is substantially later (Time 2), you may want to confirm Time 2 if it is workable for you (though perhaps not quite as late as you want).
If you back out and try again, you can run the risk that by the time you get to Time 2, it will be later than you want.
But don't despair when you are booking during the most volatile time period (7:00 to 7:15 am, when you won't see a Time 1). Each time you back out and try again, Time 2 will keep getting later until about 7:05 am or so. Then in the next 10 minutes or so, there is a good chance that it will bounce back to an earlier time.
This happened to us when Slinky Dog showed 5:30 return, but some patient refreshing suddenly popped up with a 3:30 time that worked for us.
Once you confirm Time 2, you will get your assigned time (Time 3). Our experience this past trip was that Time 3 was different from Time 2 only once, and it was just 5 minutes later.