Borderlands itself is an awesome game i played through it beat my first playthrough already workign on my second one on a different character as well as playthrough 2 on my first character.

The multiplayer is fun online more or less because the enemies get WAY stronger and you defintely see alot more 'rare' enemies. Plus its alot funner because you get to play with friends of course. But the overall storyline doesnt change at all. Just people to hang out with.