I finally feel comfortable enough to report that, with a few extremely notable hour-long exceptions, Willow's sleep has improved remarkably. She either sleeps through the night or goes back to sleep without trouble. She goes to sleep on her own (note those exceptions), and she has been napping so willingly and so soundly that I'm able to stick a camera in her face and she still won't wake up.
So sounds like a good time to screw it all up by traveling a great distance and adjusting to a six-hour time difference, eh?
Oh well. I suppose beaches and doting grandparents are worth it.