I'm about to call it quits on the first day of playthrough, but just under 6 hours in and I'm still enjoying it immensely. I've just beaten
(SPOILER)The Pursuer, was a bit of a tricky fight. Died a few times but triumphed in the end.
Some comments on game mechanics below (don't read if you want to go in as a completely blank slate, I guess):
There are some changes to Estus and the Hollowing system, and enemies drop Lifegems at a fairly consistent rate, which makes keeping your health up a good bit easier. You can teleport to and from any bonfire from the get-go, which changes the dynamic pretty significantly. It seems like a lot of the changes made were geared towards accessibility to a wider audience, but so far nothing of this sort has really bothered me or ruined the experience in any way. I'm interested to see what you hardcore Dark Souls nerds think about it.
This game will consume me.