My brother is in the same boat as you - got Demon's Souls about a week ago in preparation for Dark Souls. Because he heard the horror stories, he played very carefully and cautiously, and as a result, hasn't died all that much, except during the Firelurker boss fight. Some people just "get" the way you are supposed to play it and have a high tolerance for set-backs. The number one cause of death in Demon's Souls is trying to rush through sections because you are tired of replaying them. My brother doesn't do that - he belongs to the old school gamer type, who will simply play until the game has been beaten, and he always plays cautiously, so the game has not been a nightmare for him. In fact, he's enjoying the hell out of it and has experienced very little frustration with it.
I, on the other hand, being the younger brother, do NOT have the patience to handle a game like Demon's Souls. I've died so many times, because I always get impatient, reckless, frustrated, angry, or tired when I'm going through a section that I've gone through a dozen times before. Demon's Souls is an incredibly tough game for me, and I don't think I'll ever beat it. My brother on the other hand.... well, he's never met a challenge he hasn't beaten. He's just that type of gamer - the type who learns the meta-game, the A.I exploits and the "strategy" of getting though a game like Demon's Souls. It's almost a puzzle-fighter, in a way. Every monster, every boss, every area requires a certain strategy, and those who can pick up on that quickly face little difficulty. Those who can't, like me, find it agonizingly difficult.