Apparently I'm one of the few people that didn't have any problems with the PC port. I thought it was a great version and had no issues at all. My guess on the whole Far Cry 2 guards respawning thing is you get nothing for killing them in Far Cry, while in Borderlands you get xp and a chance of loot.
I totally get why they do the respawning feature in loot RPGs for people who want to grind. But the way it's done in Borderlands 1 is you can be in the same area and they respawn, which feels more like a bug/glitch than a design decision.