Really enjoyed my stay at the Madonna Inn. My room (Rose Room) wasn't quite as unique as I had hoped, but it was large and comfortable. The facilities were nice, the food solid and staff accommodating. The restaurants were packed on Saturday night, so I'd recommend reservations if you want to eat there. The pink champagne cake was quite delicious.
It's definitely worth a 1 night stay as you wind you way up/down California. I recommend checking out the Sunset Drive-in movie theater just a mile or so away as well.