Brick and Mordecai actually add a whole lot in rounding out the 4 original characters, and are supposed to be the comic part. Roland is supposed to be the straight man, which Kevin Hart cannot be. Kate Blanchett is a beautiful, fantastic actress who is simply too old to be Lilith. Krieg is an AMAZING character who should be added in AFTER the setup has been well established. Jack Black is an interesting choice for Claptrap- who is so often the butt of jokes, not the deliverer- but I am consistently impressed with him, so I can agree with that casting (cautiously).
The music, while a fun song, is simply wrong for Borderlands. And the failure to start with Markus doing the intro was simply a bad choice. He is an amazingly fun character who does a whole lot with a little.