Just read this post's title again, and then go to whatever website you use to check movie times and find out when/where it is playing and plan to go. Then, on Friday, go.
I saw the movie during Comic-Con in full, with an introduction and followed by a Q&A session with Neil Gaiman, who wrote the original book and produced the film and Jane Goldman, who wrote the screenplay. The movie is really terrific--don't let the big budget scare you away. It looks fantastic, the acting is great, the music is lovely (and swells a lot). For those of you who want to take the book purist approach--yes, the movie is different than the book. But the author worked very closely with the production the entire time, and honest-to-goodness likes it! Including the changes!
For more information, check out the official Stardust website.
If you want to read Gaiman's opinions for yourself, check out any post from his journal for the past two months or so.
If you need another reason, how about "because there is a meteor shower this weekend, and the movie release lines up with it coincidentally and that's really cool?"
Go see it! I'll be there!