Here's our 2 cents worth:
We booked REAS for our upcoming January Magic cruise. This is our fourth cruise, and the first one that we booked the REAS package. On our first three cruises (Eastern Magic, 3-day Wonder, and Western Magic), we were able to get Palo dinner and/or brunch, and spa reservations, but we did not always get our first choices even though we got to the port early (10:30-11:00) each time. We ended up having to modify some of our plans based on the times we got for Palo and the spa, but everything eventually worked out fine. We decided to book REAS this time so that everything was taken care of beforehand, and we did not have to arrive early at the port and wait on line to board. Also, we will not have to use the first hour or so of boarding to make all of our reservations. We will now be able to arrive at the port after boarding has started and, hopefully, walk right on the ship. We'll then go straight to lunch, which will be about the same time that we've eaten lunch on our prior cruises, but we will not have waited on line for an hour or so at the terminal and then waited at the spa and Palo for reservations. Therefore, REAS seemed to make a lot of sense for us. However, I do agree that if you are not interested in the massages, or if it does not matter too much which days/times you get Palo or spa reservations, then REAS may not be worth it for you. As long as you get to the port early, you should be able to get something. Even if you don't, you may be able to get something during the week if there are cancellations, which usually happens.
Good luck and enjoy your trip.