There are definitely Pythonesque moments- knights playing hide and seek, a herald endlessly pontificating as the king repeatedly tries to speak. But the film really has Gilliam's distinct mark. It is funny, but not as funny as you would think, and downright foreboding in places. The progression to Time Bandits and Brazil seems natural and obvious if you start with Jabberwocky.
The Jabberwocky itself is entirely convincing in the context of the film, despite technological and budgetary limitations. The scene is even a little nerve-wracking.
The ending is lovely, and again reflects Gilliam's tendency towards the bittersweet. Gilliam rarely allows his characters the happiness the audience wants for them, but he often does give them what they deserve. It can be unsatisfying at times, but upon reflection I often have to admit that Gilliam's characters' fates seem appropriate given the decisions they make and their particular approach to their individual situations.
I was not sure what to expect beforehand, given it was Gilliam's directorial debut, but I was surprised overall at how good it was and how many, even that early in his career, recognizable elements there were.