Who need plot when you have guns? Lots and lots of guns....
First, The Cons:
Lack of plot: I played through the game, there is little to no connection to the npcs around you and little motivation to actually complete missions. You find your just completing missions in order to level up your character, which is fine, but is quite unfulfilling. I would have to say the worse part is....
The variety of the landscape is limited: If you progressed in the game and visited varying environments the game would be much more interesting in my opinion. But simply put, i can hardly tell the difference between what the first area of the game looks like and how it differs from the later areas.
There are too many guns!:
Maybe i have just been overloaded by the amount of weapons in the game, its hard for me to really get excited about finding a new gun from a boss fight when i could possibly find one just as powerful randomly in an enemy peon. It makes killing bosses, or even exploring a little less interesting, seeing as the environment varies very little, and whats the point of busting your butt to the treasure at the end of the tavern full of enemies, when theres just as good of a gun in the bush?
The pros (put simply): I know alot of people who enjoy Borderlands, as well as myself. The rendering of the characters and environments is comical, charming and cartoonish. The gameplay is just plain fun as well. Getting headshots is so very satisfying. I think i have missed a large dimensions of borderlands since i have not really got to play online, but when i play split screen with my friends its always great fun. I recommend renting it first, than deciding.