Qwertyman: Damn, I didn't know they were going to add more games to that list. I assumed it was static. I had about 8 of those 5 dollar coupons and used them all, otherwise I probably would have jumped on that X-Com deal.
carnival73: I should warn that X-COM is Vista and later only.
I'm using XP so I ended up getting stuck with a useless $20 key.
Ah, that sucks, sorry to hear that. Are you saying you already used the key or you still have it unused? If you still have it and want to possibly trade for it, let me know.
StingingVelvet: Oh man, Dark Souls or Borderlands 2? That's a rough one for me.
BL2 is still really fun alone, but I think the BL games really come alive when co-op'ing with at least one friend. If you aren't going to co-op, you may get more enjoyment out of DS. Both great games. Also keep in mind that DS is a complete purchase, whereas if you end up enjoying BL2, you may end up spending more money at some point for the DLC.