I thought the Imaginarium of Dr Parnassus was bloody wonderful, but it has many of Terry's interesting problems that he tends to build into his movies.
For a start it is perhaps too complex and rich. There is sometimes things going on in the background and indeed, the foreground which can be confusing and you always suspect that you've missed something. The first 20 minutes are a bit confused, but I suspect that these minutes have been nailed on at the beginning so that some of the other features (such as the changing aspects of Tony) that were introduced by Heath Ledger dying during filming are more easily explained later in the movie. This, I think will turn off some people and they will feel that the whole film is confused, but it isn't really.
Some of the visuals are spectacular. Some look like he has raided a country school theatre cupboard and thrown the results onto his actors. Some scenes have a distinct feel of Brueghel about them, others more eastern and mystical. Some bits are not explained at all and you are left with a "what the hell was that" feeling. For example - who was Percy as a character and why did he seem to know what was going on all the time??
Overall it is just as good as Time Bandits, complete with the a (probably slightly less) ambiguous moral ending that is his trademark. At its core, it is a simple morality play with the message "be careful of your choices as you will have to live with them". Though it does have a definite, satisfying ending for most of it's characters.
Personally, I loved it.