It is far better than Shaun of the Dead IMO. Shaun was very slow to get going and then the ending, it was frustrating. Zombieland is more light hearted, yet gorier (weird, eh?) and is WAY funnier. It's one of the most inventive movies in recent years. You very rarely get narrators anymore, and the on-screen Zombieland Survival Rules pop-ups are so hilarious. I've seen it twice, may even see it again.
And Woody Harrelson turns in what may be his best comedic performance ever.
Definitely a DVD-worthy purchase when it comes out.
Oh, and a special star cameo that took everyone by surprise. Beyond funny.