I really liked this film. It is similar to other Terry Gilliam films in that there is some sort of morality play as the underlying theme, but it is the interesting characters, the stunning visuals and the odd humor that make his movies fun IMO. Fans of Monty Python, Time Bandits, Brazil and Baron Munchausen will likely enjoy this one and you have an idea of what to expect: unusual and unique. This one is a pretty straight good vs. evil "chess match" as it were, where the two sides are making wagers and competing with each other to win those bets.
I am a fan of Gilliam's work, but I also wanted to see it because it was Heath Ledger's final film. I always enjoyed his acting. The way they handled it was cool, by bringing in other actors (Johnny Depp, Jude Law and Colin Farrell) to play the part of his character in different "through the looking glass" world sequences. Each of them steps in for a particular scene and performs it in their own way. I thought it would be weird, but as the circumstances are different for each sequence, it worked. They said they had pretty much shot all of the "real world" scenes with Heath so it was an interesting way to handle the loss of him as a main character and it is sort of a way to pay tribute to him. It adds a whole new element to the movie.
It is mostly dark visually, with some of the Imaginarium scenes popping with bold colors in a Willy Wonka sort of way. PQ and AQ are good. I give it a 4 out of 5. Recommended. I'd still call it a rental for most, as Gilliam's films tend to either be loved or hated.