Well, I've made it to Anor Londo with my Caestus only character. It's really fun, and not as challenging as I would have thought. Still difficult, but not overwhelmingly so. Killing things with just your fists is so satisfying...I managed to beat the Stray Demon on my first try, which surprised me. Usually it takes me a few tries on a regular character.
They don't do a ton of damage, but they're fast and don't use a lot of stamina. I've found I can usually spam a bit and stagger the enemy, and then really punish them. At +15, the Caestus does decent damage.
I think the hardest part is no shield. I'm getting pretty good at parrying, though. Finally. I've always been pretty bad at it.
Also, I think Dark Souls has officially become my most played single player game ever. (Well, I guess it's not technically single player. But I'm ruling out games like TF2, etc.) That's pretty crazy to me. I just don't really have a desire to play anything else lately.