I don't want to say too much about the movie itself, since I've read so many reviews of it that give away little bits of the joy the movie offers (and really, movie critics who give away twists of films they're reviewing ought to face some sort of punishment; that shit happens all the time, and I can't count how many great scenes in movies have been ruined because a show-off critic just couldn't help him- or herself). But I will say that Basterds has to rank up there with the best Tarantino has done so far. He makes entertaining movies that are more fun, more fucking delightful and mesmerizing, than anyone else, and by that measuring stick, Basterds is as good as he's done. Pulp Fiction is my favorite Tarantino, but I'm really not sure that Basterds isn't just as strong (time will have to tell, since I just got out of a showing and am still a little buzzed from the experience).
I should also point out that if you're worried about seeing this because you think it's too gruesome, don't be; there is some gore, because that's the kind of director Tarantino is, but there's probably a lot less than you're expecting, and unless you're really, really squeamish, you're denying yourself a fantastic moviegoing experience by not going to see this.
One last point: if you're going to see it, see it in a movie theater. This isn't just a movie about World War 2, it's a movie about movies, and waiting for it to come out on DVD is just fucking wrong. Plus, I'm thinking it looks a lot better on a big screen, sounds a lot better on a big sound system, and is a lot better when seen with dozens of other souls in the room.