I read this a long time ago and this time--as I work my way through this book-- I'm impressed by a number of things: I'll be fairly general here so no spoiler tags should be necessary.
First there is the sheer intellectual brilliance of George Eliot. One is always aware of a powerful mind organizing and controlling the vast canvas of this novel. But for me an even more impressive quality is her ability to create sympathetic, complex characters whose belief systems and social attitudes may vary significantly from her own. This ability to focus with a compassionate understanding is something I find very moving.