We did just last week.
I combined an RCI trade, and my own DVC points at Saratoga last week. I made sure to let the front desk know, as I did not want to change rooms. We did not have to go get new keys as keys are now on the Magic Bands. Early in the am of our RCI check out day, I got the receipt for my room email, then a text saying my room was not ready yet, then almost instantaneously was a text that had our room number and location. Our bands worked.
The only complications were the rooms were in my name and then my Husband's name and the front desk said it may have happened automatically if everything was under the same name, Also, Housekeeping was somewhat confused about what should occur on our RCI check out day. I called Housekeeping to check what would happen, and the manager there told me the room was clean, however, when we returned from breakfast, there was a basket in front of our room as if it was ready to be cleaned. We did not get the room cleaned (put the do not disturb sign on the door) since the points extension was only for 2 nights. But did ask for additional TP and dish washer packs.
I was impressed, this was the easiest extension I have done, in the past, I have done cash, DVC cash and even an Expedia (or Orbitz?) reservation with points and always had to go to the front desk, explain things and still not be sure if we had to move or not.