Loved it. Fantastic, mind-blowing ideas and many-layered cultural setting, social systems, and characters. My only complaints are 1) the dialogue comes off as stiff and overly-constructed (which I assume I can attribute to the difficulty of translating from Chinese), and 2) the exposition and plot advancement (especially as we begin to learn more about the Trisolarans) often feels very heavy-handed.
Some of the best science fiction I've read in awhile. Will definitely read the sequels.