Well, I've never been much of a Tarantino fan. I enjoyed Pulp Fiction and Death Proof, but I never saw them as the masterpieces they represented to some. This movie changed that for me. I actually saw and understood the genius in this movie, and there's plenty of it.
First of all, the acting is brilliant, especially the Nazi officers. It is always spot-on and fitting to the mood. Next, the music is among the best-used music I've ever seen in a movie, although it often ends abruptly (I guess that was on purpose, and it does still work). The cinematography here is leaps and bounds ahead of anything I've ever seen Tarantino do. It's beautiful from beginning to end. And finally, of course, comes the script. By being a bit more conventional, he knocked it out of the park. I was fascinated from the very first second to the very last, and the 2:30 hour movie felt like it lasted barely an hour. The plentiful dialogue is brilliant and well-written. The actual story elements swung me through a vast array of emotions; be it stress, horror, glee, confusion or "Holy-crap-this-is-awesome"ness, I felt it all. And of course, the ending (I consider the last 20-ish minutes as "the ending") was genius in its own right (I can tell you that you probably don't expect it, but at the same time, you kind of do).
On the downside, it's very violent, and I can definitely see that my own tastes in regards to this movie will not be shared by everyone (that's Tarantino for you).
In a sentence:
Brilliantly shot, written and acted, this is the first movie from Tarantino that I could actually consider calling a masterpiece.