It's dirt cheap and a great game. I say go for it because this may be your last chance to play the first game with a lot of other players. People tend to play through the previous game just before a new one gets released.
I could never get burnt out on borderlands. It's always in my system or close by when I get burnt out on other games. The first one is a must play. It's one of those awesome titles that no matter how much you play it it's always fun.