Well, I can now say I've seen Cambodia's most famous attraction: Angkor Wat. It's in fact a collection of hundreds of temple sites, Buddhist and Hindu. We spent one day exploring smaller ruins, which were truly overcrowded by tourists, mostly Japanese and European. There's been decent preservation, and one of the coolest parts was seeing enormous ancient trees whose roots had been incorporated into the walls, but overall, the sites didn't feel very spectacular or spiritual.
What was really amazing was seeing the main Angkor Wat temple at sunrise. We woke up early to get there, and entered the main gate while it was still dark, so as we watched the sun come up, we had no idea what we were surrounded by. I got the chance to wander around inside the main temple's corridors before the crowds made it there; it was beautiful in the early morning light.
Definitely worth the early morning!