In my opinion, I don't believe it is a hard game but I can see why most people THINK it is a hard game.
It is not a hard game to me because, as many others have pointed out, the majority of the monsters/levels are all easily beaten if you know what attacks the enemy does and what they're weaknesses are. Granted, to get that knowledge you have to die a few times :)
Why I think some people think the game is difficult is the "no checkpoint and all monsters respawn" aspect. They think "it took me 30 minutes to get to this location and now I have to do it ALL over again!?!?". I guess they don't take into account new info learned (or fail learn from their deaths). If you do take into account and learn, it only takes a fraction of time to get to the point again.
I also think people believe it is difficult due to the fact that certain armors/weapons are better against certain enemies as most gamers don't like to think about the situation and like to just use the same equipment, always. I also don't think people like that the fact that most enemies can kill you in DS in 2-3 hits though, if you pay attention, you shouldn't really be getting hit too much.
I mean, I can run through the whole game with < 25% health (so I can use the...rat's ring or whatever to drastically increase damage) and not die more than a few times. It's not THAT difficult outside of a few bosses (man eaters...I'm looking at you).
