The difficulty isn't the issue, although presenting the player with some fantasy monstrosity that fills the entire moveable area without any clue as to what you can do to avoid him or falling to your death is pretty stupid. The big mistake the game makes is that assuming the player is in the exact position of the character. I have situational awareness as a human being so that if i'm stood on the edge of a cliff i KNOW it. If i'm playing a game that isn't there, even if i can see that i'm on a ledge or something. That's why games have things like invisible walls. i've already been knocked off some stairs by a trap - and survived only to find i can't get back so i had to suicide and lose all my souls. Pretty stupid.
But for me the biggest issue is the simple placement of bonfires. Sure the enemies are rought, and that's fine. But forcing the player to go all the way back to the last bonfire, which was miles away, every time, is just retarded. There's no getting away from this. At least placing a bonfire right before every boss fight would have been the minimum i'd expect. In fact i'd go so far as to say that if you are going to make a challenging game then you as developers have got to up your game: you have a responsibility to give the player all the tools to interpret that difficulty: the camera has to be spot on, the lock on system spot on, the framerate spot on. Everything has to be there. I'm not saying it isn't, but there are times - especially with the great big bosses that come up short just because it's so difficult. It's no good putting the player into a position where he's getting sniped by things out of camera range, or by firebombs that are being thrown by people inside a room you can't get inside to see without first being firebombed. That's poor design.
I'm not going to say it's a bad game, and even if i did it would be pointless. But I'm certainly not going to say this is designed as well as it should have been - not could have been, but should have been. Especially for all the praise it's gotten. These reviews are writing cheques this game isn't cashing.
As for me; i'm currently in the undead burg. I made it, with about 1 point of health, to the Taurus demon. It killed me. I have no idea how you fight it and i'm not going to get the chance to learn without first going all the way back to the bonfire (which i'd done about 6 times already) in the burg. That's not a learning process that helps the player learn to fight the boss and tha'ts why placement of checkpoints is critical.