I will just start with some quotes from other reviewers that describes it the best.
"This is easily one of the most overrated films of the year and probably the worst film Tarantino has ever done." "The ONLY good thing in this movie was the performance of Mr. Waltz".
"So I was really disappointed, and seeing this movie on place #40 of the greatest movies of all time is the only thing about this, that leaves me with my mouth opened" Now for more details go and read "Hated it" reviews.
One thing I hate about a movie is when it treats audience as bunch of dumb people. (Spoiler ahead). Now I know Tarantino's style is based on fantasy and fictitious plots, but come on, Adolf Hitler and 200 top Nazis Officers will be in attendance of a movie premier in occupied France and you have only two guards in the whole theater and the surroundings? Where also an American-African walks around freely with steel pipes locking doors and setting fire. These 2 guards are then executed in seconds opening the door for our 2 "heroes" to slay Hitler at point blank with around 100 rounds... very dumb. At least, challenge our intelligence and create a smarter plot to kill one of the most feared tyrants of all time (Go watch Valkyrie). Besides, Mike Myers impersonation of a British general is more realistic and authentic than the guy doing Hitler, just picture that.
What ruined it further, is that the only smart and powerful character, which nailed everyone in the movie, with his psychological and mind bending interrogations, ends up to be effortlessly tricked by the most mindless character in the movie.
After watching the movie, I was sympathizing with Nazis, who were portrayed to have more bravery and humanity than our Basterds!!! Imagine that.
My recommendations, if you have insomnia, 2hrs 33 min to waste or you want to give your mind a break, go watch this movie.