My wife and I watched this for the ~5th time last night and it's so freakin good. Literally one of my favorite films of the last several years. It's one of the most romantic films I've ever seen, but it's not strictly romance. There is a supernatural mystery and a race against time. Despite having seen it a few times, it's still every suspenseful.
I also think it really benefits from rewatching. Once you understand what's really going on, you can go back and pick up on a bunch of little details that add to the story throughout. So, rewatch it if you've only seen it once.