So, today with enough leisure time, I decided to do it and popped in Dark Souls to my 360 and take my first steps in it. I got to play a solid, uninterrupted hour or two.
The initial impression is underwhelming. Early 90s style menus, a bit underwhelming graphics. The movement and combat felt initially sluggish, reminding me of Monster Hunter. No directions, no signposting.
Slowly I started to get hang of it - keeping up the shield, as GAF suggested. I learned that the combat really wasn't sluggish but actually represented the weight of the weapons I used, so I needed to compensate for them in planning my attack. I learned that different enemies had different attack patterns and behaviors that I could memorize.
Quite soon after the beginning I belive I got what it's all about. There was a dragon boss, much stronger than I was, seemingly able to whack me on a few swipes. I kept on going back, getting my lost souls, trying again. I learned that I need to focus on the dragon, roll sideways when the hammer comes down, and backwards when the dragon jumps. Also, I was best finding my way behind it. Then just doing a quick strike, not getting too greedy with multiple strikes.
Completing the dragon took me some 10 tries (I haven't learned how to use the potion), but like people have suggested - each death was my fault. The sense of accomplishment I felt when defeating this one very early boss was incredible. It was a real effort, but I practiced, planned and did it.
It seems I need to be constantly alert and focused, my mind can't wander anywhere else while playing.
So, that was my first hour or two with Dark Souls.
EDIT - I went for Pyro / Master Key by the way. I hate looking for keys.