I found it to be a visual spectacle worth seeing. Ang Lee has used the 3D medium fantastically and created a treat for our eyes.
Do not see it in 2D - 3D is the only way to go.
The story is interesting as well. I had not read the book beforehand, so had gone in with a clean slate.
The story is told in flashback mode by the senior Pi Patel (Irrfan Khan). When he was young, Pi is introduced to multiple religions, and his experiences help him later in his life. This does not go too well with his "rational" father, but he does not get in his son's way and keeps on teaching him useful things anyway.
The main story happens on sea. When going with his family to Canada on a freighter, the ship hits a freak storm and starts to sink. Pi manages to clamber aboard a lifeboat, with a tiger (called "Richard Parker") who also survives.
Pi's epic 227 day struggle for survival in the ocean, with just a tiger for company changes him drastically. What he experiences takes him closer to God, and the whole philosophy of the "nature" of God.
The new actor, Suraj Sharma, has done a very good job. His interaction with the (CGI) tiger, are the "meat" of the film. Some are funny, some are intense. The tiger has been captured extremely well and makes you feel that he is almost human - lovable at times, and frighteningly predatory at others.
There is a heavy dose of spirituality, esp. in the beginning and end of the film. Some may like it, some might not.
We are told another story about the same sea saga later. Nobody is sure whether the 1st one is correct, or the 2nd one, a mixture of both, or none of them happened. But the beauty is that it doesn't matter.
The main reason for recommending this film is Ang Lee's direction and fantastic use of 3D. The colors in India and the ocean are shown vividly. There is an extremely effective representation of the storm - water is tricky to get right in 3D, but Ang Lee has mastered it here. The tiger is shot very well - a combination of (supposedly) 4 Royal Bengal tigers and CGI effects. The luminescent shots of the waters at night, and the whale arising majestically out of the water. All will stay in your mind long after the movie ends.
See it just for Ang Lee's craft. If the story gets to you, it is a bonus.