It's surprising to me that "Eternal Sunshine of the Spotless Mind" made its way into theatres with so little attention, especially since the writer is the same person behind Being John Malkovich and Adaptation. That said, it's better than either of those movies.
The premise of "Eternal Sunshine" is simple -- what if you could erase the memories of a painful relationship? That said, the characters in this film are emphasized a lot more than its sci-fi premise. Like Malkovich and Adaptation, it's an amazingly clever and creative movie, but there's far more "there" there.
Both Jim Carrey and Kate Winslet are excellent in their roles, in part because there is so little obvious "acting" or hamming it up going on. In fact, all of the characters in this movie feel uniquely human, uniquely special, and uniquely flawed. This allows the director to switch emotional gears effortlessly, from happiness, love, humor and fantasy, to dark humor, pain, hopelessness, betrayal, failure, and the hard and sometimes ugly side of relationships.
Ultimately, it's a thought-provoking, real, and ultimately redemptive movie about relationships. Definitely worth seeing. It's getting impressive feedback at IMDB (8.3 rating) and at Rotten Tomatoes (94% fresh)... hopefully it will get the audience attention that it deserves too.