Dear lord I just had the most tense fight with a Black Phantom in my entire Dark Souls career. I was in a pretty secluded room that you can't easily reach, so the guy spent like five minutes looking for me, as I was looking for him. I would sometimes see the guy run and get into a hallway, only to lose him as I got to where he was. We finally found each other, dueled, I got destroyed
PVP is pretty hit or miss right now. Probably has to do with my ping, but I'm never completely sure my attack landed or not, and then there's the lagstabbing. The DLC area is pretty fun for this, though, you get invaded quite a lot.
I had the craziest PVP fight ever... I was dueling a guy in Undead Burg when I got invaded by another red phantom. The honor-less bastards both turned on me and I got backstabbed by the guy that I was originally fighting. I started fighting them BOTH lol and I prevailed!!! (of course I used healing items since it was 2 v 1) I killed one guy with a great chaos fireball and killed the second guy with my Chaos Blade... this was the best feeling I've ever had playing any videogame. Holy shit lol.