We did it out of necessity We had to add one split-stay night at the beginning of our trip because our main resort wasn't available when our plans changed. Never got the room ready text from the first resort, and I had to call and talk to the "front desk," and was told the text should've gone out hours ago. Great. We just wasted several hours waiting and got our room assignment too late to get to MK for the evening.
The transfer of bags/Owner's Locker went smoothly, and our MBs worked on the door after we received the online check-in text early-afternoon that our second room was ready.
Our credit card, however, wasn't linked to our second stay even though I checked in online, and we didn't find this out until we tried to charge the first time that evening. Calling the "front desk" at PVR/PVB proved a giant circus, as when I gave them my number, they said they couldn't do it over the phone and we'd have to walk all the way back to the lobby (our room was near the TTC) just because they couldn't figure out how to add the card. After a couple more calls, I got someone who actually knew how to do it (I thought Disney made it easy to take money), totally contradicting the other dumb CMs I'd gotten before.
And this is one of the big reasons why I didn't care for the split stay. While attaching a credit card is/should be an easy thing to take care of with one call, you double the chance of having to interact with a clueless CM at the front desk or on the phone. I have almost zero faith that the online check-in system will work when I utilize it, and dread even more having to talk to a CM to clear up any glitches. They're sure good at saying, "I'm sorry," however. Seems to be the only consistency with CMs property-wide.