If you have the original Borderlands, Gearbox released an "Enhanced" version of the game a couple of weeks back. Graphics upgrade, some new weapons, a minimap (yay!) and some other stuff. And all for free! Check it out, it might make the game worth replaying.
EDIT: I checked my Steam account, and the new version of BL was already on my games list and awaiting download. "Borderlands GOTY Enhanced". I downloaded it and played through a few missions. Graphics are better, and there are some welcome gameplay tweaks, like auto pickup. I don't know if I'll play through the game again or not, I pretty much wor e out the original. Still, you can't beat free.