I've finally seen it, along with a few other Miyazaki (princess mononoke, nausicaa, majou no takyuubin...) and it's the best for the music, pictures and general atmosphere.
What I like best in this one is the traditional atmosphere with temples, bath houses, etc.
There was a programme on Japanese TV about "Sen to Chihiro" that was showing the English and French dubbing. The voices are very different in each version, which changes the general feeling of the movie. From the little I've seen of each trailer, I prefer the original in Japanese (I don't like the English "r" in "Chihiwro", for instance).
In the same programme, they surveyed children around the world and asked them which passage they'd liked best or found most impressive. In Korea, it was the one where the parents were turned into pigs. In France, it was the passage with Chihiro riding Haku as a dragon and remembering when she fell in the river when she was a child. Personally, that's the passage like least in the whole movie.