Is it a comedy/action thriller?
A horror movie?
How would you classify it?
All of the above. It's not very scary (I guess if you have a thing about snakes). There is a lot of humour (you'll think twice about joining the mile high club).
Action wise it really doesn't let up. The things a roller coaster from start to finish.
Of course if you go in there with a penchant for picking holes in scripts and / or you are unwilling to suspend disbelief for an hour or two, the movies not for you.
It's fun. I saw Dead Man's Chest this summer and felt (as does my wife) Pirates doesn't even come close, for popcorn entertainment this is the real deal.