Dark Souls is goddamn fucking amazing.
To put that another way... it's Demon's Souls to a T. They didn't fuck with the formula, they took what worked, and did it again. And frankly, if they do this another ten times, I'll buy every single one of them.
I'd write up a full length review, but it seems sort of pointless since I already did that back when I started playing Demon's Souls a couple years ago. The bottom line is, if you loved Demon's Souls, you'll love Dark Souls. If Demon's Souls didn't sound like your cup of tea, stay away from Dark Souls.
They didn't make it any easier. They didn't make it newb friendly. It's a hard game, with a practically nonexistant tutorial. You're not going to know how most of the in-game mechanics/systems work, and because the game just launched there isn't a lot of "cheat" material online. That's all part of the appeal for me, but if you just want to sit back and be entertained, look elsewhere.
If you want a challenge, however, you'll be hard-pressed to find one as robust and rewarding as Dark Souls.