Grindhouse is really 2 movies.  Robert Rodriguez and Quentin Tarantino teamed up to make 2 B-movies, complete with worn out film and cheesy previews in between. 

The first move is Planet Terror, a zombie movie (Rodriguez's movie).  It was a great on-purpose B movie!  There were times I was starting to go, "like that could really happen" when I remembered it wasn't supposed to be believeable.  A lot of the on purpose mistakes were funny.  There were tons of random explosions.  And there was a high gross out factor.  (There were a few times the audience audibly gasped.)  All in all, it was a fun movie.

The previews were great!  And hilarious!  I think they were trying to one up each other for the worst movie based on the preview.

The second film was Death Proof, about a stunt driver that kills young women with his car.  It starts out very B-movie, but as soon as the action starts, I think they forgot it was supposed to be a B-movie and instead turned into a regular Quentin Tarantino movie.  It was still very good, and the ending was awesome!

As good as Grindhouse was, I probably would not recommend seeing it in the theater.  If you would rather see it now instead of waiting for the DVD, see a matinee or at a second run theater.  The exception would be a drive in theater.  This movie would be awesome to see in a drive in.  I plan to buy the DVD, and it'll be a great movie to see with a room full of friends so you can comment and talk about it when it's on.