The movie is pretty good for what it is.  My experience coming from reading the novelization is that they left a whole lot of cool stuff out.  There is a whole bunch of magic that just does not show up, as well as some really cool creatures.
I also finally figured out what was bugging me about the movie.  You can see the directing!  There's a scene in the novelization where Marique is taking off her father's armor while they talk.  This scene was used to play up that creepy angle they have.  In the film, the scene starts with the camera moving into view of Marique and Zim, you can clearly see Rose waiting till she's in full view of the camera to star caressing the armor ... but she was talking still before the camera got to her.  It was one of those "gosh, I gotta go act now" moments.
There was also a movement on the boat where from one angle Conan is standing straight up (when shown from behind), but when shown in the same position from the front he's slightly bent over in the same scene.  Bad editing, bad directing?
There's a whole bunch of moments in the film where you can see the directing and the acting, but I give it a pass for Zim and Marique because what they were doing was grand theater, big strokes, very impressionistic.
Jason owns the movie though.  The way he moves around even in a more passive scene.  There's a pent up rage always going on there that is quite good.