I'd heard that Dark Souls is hard. After playing through the first section of the game, so far: it's hard.
How is it hard
The numerical abstractions are pretty thin on the ground! You deal certain amounts of damage, enemies have certain amounts of hp, but those formulas only clash if you get past the hurdle of movement, positioning and so on. It's very much an action game; I've seen hints of a lot of rpg mechanics to come, but those will just add complexity.
I don't yet know if this holds true for the rest of the game, but the distinction between 'normal' and 'boss' enemies is huge. To fight just the first boss, who I assume is a cakewalk if you're used to it, I found that I needed to both think and practice, putting together unfamiliar controls in relatively complex sequences. Relative, that is, to other modern action games, which tend to ease you into this sort of thing with endless tutorials and difficulty ramping.
What about other things
It's quite a pretty game, and I like the backstory. It's all very doomed and tragical; is "Undead" a translation of some slightly different concept? The first other undead guy I met was on the brink of "dying", which does not make a lot of sense.
I've got a huge amount still to learn about game systems and the game world. It's daunting, but both thematic and mechanically interesting enough to continue for now.
What do I regret
I only figured out how to jump/kick reliably after fighting that guy, so I didn't get to jump-attack him from the ledge.