Like the other reviewers I have nothing but praise for this game.
It has a reputation of being incredably difficult but thats not strictly true. There's just more thnking involved than slashing. You have to plan your attacks and take into account the patterns of the enemy and how they are grouped. Just the little things like choosing to use a "thrusting" weapon like a Rapier instead of a "wide arc" one like an axe in enclosed spaces so you don't keep wasting your attacks hitting walls.
The combat is really solid and it's good to have a game where not every foe falls with a couple of slashes. Took on a blue-eyed knight and it was one of the best gaming experiences I've ever had. He fought using cunning and tactics, even backing away to swig a health potion when I'd got him low. Because I was a lighter character I had to use my speed to flank him and stay well out of the way of his attacks as I wouldn't last long against them at all.
I love the fact that you're always on-line and other players appear in ghost form and can leave you messages. Several times I avoided traps thanks to these timely warnings...brilliant traps though they were. Clicking on a bloodstain on the floor allows you to see a ghost replay of a recent players death which you can use to determine the sort of foes you may be encountering ahead.
Oh, and did I mention the fact that it is a stunning looking game? The vistas when you break out of the dungeons are vast and gorgeous. The whole game is veneered in a fantastically epic theme, a mixture of isolation and heroic exploration. Really tense yet never terrifying.
Buy this game, you'll not regret it ... ever.