Trailers are misleading.
With Epic Movie, the trailer was better than the movie itself (which was the biggest waste of time in my life, and inspired me to write my first review for IMDB).
Since Meet the Spartans are being made by the same guys, I predict the outcome will be the same as with Epic Movie - the trailer will be better than the movie itself.
So the trailer was good (especially the Britney being kicked part), but that's all I will be seeing of Meet the Spartans.