We switch resorts on every trip and love it. Even with small kids who have always needed naps in the early afternoon, it's always worked out. We always have a rental car, so find it easier to transfer it yourself.
The only thing I've heard about Disney transfering it is that they don't gaurantee it will be at your next resort until 3pm, so other guests have suggested taking a sep. bag with you with things that you might need during the day, such as a bathing suit.
We always try to switch on a day we aren't doing a park, but it rarely works out that way. Even with doing parks, it's never been a hassle. We found it the easiest to get up a little earlier and check into the new resort then go to the park. The room isn't usually reading, but they store our luggage and we get it when we get back. This way, they know we're there and they have more time to arrange the perfect room for us if possible.