I'm just over halfway through the single player campign of Brutal Legend, and so far my impressions are very mixed.
In comparison to Tim Schafer's previous game Psychonauts, a few things are similar such as graphic design and semi-irreverant sense of humor, but the storyline is much more cliche and uncreative. In fact, for the first half of the game the story can be completely dismissed. Thankfully after the first 'big boss' is disposed of, things take a big turn for the better.
The gameplay suffers from the same slow ramp up. There are three major components to gameplay: foot combat, vehicular combat, and field missions which are a semi real time strategy minigame that hearkens back to Giants: Citizen Kabuto. In the early to mid game all of these components feel overly simplistic and generally uninteresting. As the game progresses however, upgrades become available and enemies become more interesting, greatly improving matters.
So, at this point, my disappointed optimism is cautiously returning. I'll post a full review as soon as I've finished the game!