Dark Souls so far (just made it to the blacksmith, which is neither that far into the game or much of a spoiler) is not difficult, but it is punishing for sloppy play. Grinding does, to some extent, make things easier and if I've found myself short on souls I'll experiment with different play styles (still haven't got parry/riposte right), tougher enemies (like black knights) or explore (hey, there's a merchant in Undead Burg!).
But the biggest thing I've found is that I feel like I'm a kid playing a game for the first time. By that, I mean that I don't know what's coming, have to remember not to rush ahead blindly, and I have to keep repeating the same section over and over - sometimes pushing a little further forward and others not even getting 1/4 of the way I did last time. It really reminds me of those tough games like Faxanadu, Link's Adventure, TMNT on the NES.
Don't know if I'll get sick of this or not (I had a fair bit of time to play today but most days I don't have that luxury) but for today it's been glorious.
And I've not even mentioned the joy I get from see other players appear beside bonfires, or seeing their last moments which (as I'm sure many of mine are) hilarious.
... I should've probably made this a LTTP but whatever.