I bought this game after having played the demo, which I highly recommend to avoid wasting your money if it's not your thing. If you enjoy the demo then definitely get the game, it is much, much more of the same fun gameplay with almost 100 different playable characters with many different skills and interesting levels from all 4 of the films. There is so much bonus content to unlock by collecting items and unlocking new areas, that every level has replay value.
Another great part of the game is the fact that you can play 2 player co-op all through the game, choosing to work together or just run around madly collecting coins. The split screen system works fantastically, seamlessly joining when the two players come close enough. The game is just as fun 1 player, but it's always nice to have the option for a friend to jump in at any time.
This is probably the most fun game I have played in years, and I think should definitely have been a candidate for game of the year over some bigger titles. It is very thoughtfully made - you never have the feeling that any feature was just rushed in to get the game on the shelves, and cleverly designed in terms of using lego pieces to make the props, while the other scenery is as well modelled as any other title. It is also very funny where other games are just lame.
If you are a fan of Pirates, then this game will definitely go down well but even for those not so bothered about the films, the game is just fantastic as a standalone title.