Excellent game, but playing with a friend is essential.
The simple things are amazing. Combat, weapons, artistic design are all amazing and it a,es for a brilliant game. However, a few silly things tarnished the experience. For example, the range of weapons and shields is astounding but but offering them to you in vending machines and crates at random does have its downside. towards the very end of the game you are STILL being offered weapons you wouldn't have accepted at the start at this becomes very boring and soon makes searching tiresome. The car mechanics too, for example, are very irritating. The actual driving controls are unbelievable (in a bad way) for a game soolished and fresh. Similarly, you crash on, or near, any obstacle you come across and this takes away from the game's fluidity. Finally, the long treks from place to place are downright boring as you can only fast travel from certain places. You also have to travel THROUGH a place to get to another so it causes all sorts of confusion with regards to bearing.
On a plus side, it's incredibly fun with a friend and the shooting is excellent. There aren't that many variations in mission (go find/destroy, return) but the polish really helps you to forget that.
I loved Borderlands on the whole and can't wait for the sequel.