Funny, enjoyable, and polished
Not a masterpiece, and perhaps less than I expected of Tim Shafer, but nevertheless a genuinely enjoyable, sometimes very funny game. The graphics are very good and I haven't noticed any slowdown despite often dozens of units on the screen. The world is a good size, varied and interesting, with many amusing set pieces such as Mount Rockmore, which you can customise with giant busts of yourself and your allies.
The voice acting is almost flawless, but the same lines are used often enough outside of story missions to be noticeable at best, irritating at worst. Help messages for mechanics you have already mastered are also inexplicably shown regularly in-game when exploring the open world, which is unfortunate as the complete absence of a HUD is an element which really helped me to get into the game. However these are minor issues.
As a fan of the humour of Shafer and Black, the music of Black Sabbath and Tenacious D, and games that play with the presentation of derivative game mechanics, I found Brütal Legend to be naturally entertaining, and well worth £35 for (the day before) launch day.