All the best parts of Demon's Souls, and then some, but still room for improvement (SPOILERS)
The graphics - highly detailed, beautiful and well-designed areas, etc. Not a huge improvement from Demon's Souls, but noticeable. Speaking of noticeable, thar be some framerate issues matey (see below).
The game world. It's huge, and mostly continuous. Instead of multiple levels connected to a Nexus, the world is now one big interconnected hellscape. Most of them are dark, and some are very dark. Some are staggering, like Anor Londo, and others are terrifying, like New Londo. However, each area gleefully awaits your many demises.
Bonfires - O thank you Gwyn for these wonderful waypoints. Seriously, these made the game so much better. Now, instead of only getting a waypoint after defeating a boss, there are now bonfires that can be lit and kindled throughout the world (except New Londo, but the absence does fit the story, grumble grumble). These bonfires also serve as a place to upgrade/repair gear, as well as level up and recharge your healing Estus flask (so long herbies). Be warned, however, that resting at a bonfire resurrects most enemies in an area. Also, on a related note, quitting the game no longer sends you back to the last waypoint. Thank you From Software for acknowledging that we humans often have life events that take us away from the game unexpectedly.
The sound - music is subtle and moody, and voice acting is well done.
Items - tons of weapons and armor, all upgradeable in their own way. Although, I'll admit I played half the game with an armor set I got early on and upgraded the hell out of. There are 4 blacksmiths now, all with unique forging abilities. There are myriad rings that confer all sorts of benefits, but for a being with 10 fingers humans are still restricted to two rings. And necklaces/amulets? Fuggedaboudit.
The online play - much the same as Demon's Souls. As much as I *hate* being invaded, it's a lot of fun to call in reinforcements and leave messages. Protip: disconnect your interwebz if you want to enjoy the benefits of humanity free from the risk of invasion. What's new about online play is that many are now tied to Covenants. Some allow you to invade more readily to commit your sinful murder, others allow you to exact retribution or to protect sacred areas. There's even a covenant that boosts players' miracles if other players are online in the same area using it. If you like PVP, this game offers plenty of it. Protip2: keep your level low and max out your gear.
The challenge - this game is very hard, especially at the beginning. You're going to die frequently, you're going to agonize about whether to turn back and cash in souls or press on and risk them all for more. You'll not get lost often (Duke's Archives confused me), but you rarely get clues as to which area to visit next. Don't worry, how easily you're annihilated is a clue.
The character plots - not much to speak of here, but I like what there is. There are several NPCs with story arcs that depend on your actions. While they rarely offer any clues whatsoever (and some outcomes are far more beneficial to you than others), it does create a grounding sense to your actions. Unfortunately, most of them end up Hollow and need to be put down, but hey, at least you then get to loot their corpses free of sin.
Dark Souls is enormous. My first play-through took 110 hours, and I did only enough soul grinding and titanite farming to get by. This enormity (coupled with the relative non-linearity) makes it so that, without a strategy guide, everyone will have a unique playing experience. If, however, you have a OCD tendencies and want the best gear upgraded to the max, you best buy a strategy guide.
The size of the game means you're going to do a fair amount of walking. I'd recommend investing in a constant supply of Homeward Bones early. The warping ability that is acquired midway through the game is not very comprehensive and sometimes opens places you have no need to visit again. To me, any activated bonfire should have been warp-friendly. The warp ability feels like a late addition; why the hell else would you warp to the gravelord site, which only becomes available after you render that area completely useless? And seriously, 3 warp sites in Anor Londo? How about just one in the Darkroot area, or one near blacksmith Vamos?
The worst part of the game is the frame rate issues. On my PS3, the original 60 gb model, I had noticeable and persistent framerate issues in Blighttown and Lost Izalith. In both cases, it really killed the immersion. It feels sloppy, like they didn't test it out enough on the final systems.
Snuggly - from what I understand Snuggly the crow could be gifted infinitely until one of the more recent patches. That means there are some players who were able to acquire a huge amount of rare items that should have been ones-off. I don't know how the devs screwed this up - Sparkly the crow only allowed for 1 trade in Demon's Souls.
However, my biggest frustration was the occasional freeze. This happened at least a half dozen times, and it was infuriating. In most cases, the game saved and I was able to recover my game after re-booting the system.
The story is pretty thin, and it doesn't wrap up in a very satisfying way, regardless of the ending you choose. I know the Souls games are supposed to be more about the journey, but this one seems even more nebulous than Demon's Souls. The last thing I want after such an arduous journey is an anti-climactic boss fight followed by self-immolation.
Also, as much as I love the gear upgrading, The materials needed to upgrade armor and weapons are, IMHO, a little too rare, necessitating extensive farming in select areas. You aren't getting a set of +10 armor just by playing through normally. Twinkling titanite is a perfect example. It's needed to upgrade all advanced armor to +5, and there's only two places to farm it: one takes forever and the other takes forever to get to.
Humanity rarity - seriously, how many rats do I gotta kill?
My last gripe is the tracking arrows from the enemies. Seriously, that's just cheap. It was cheap in Demon's Souls, and it's cheap in Dark Souls. The game is plenty hard without tracking arrows.
With all the above gripes, my relatively high score might seem off. However, I tend to criticize the games I love the most because perfection is within sight. The Souls series is now on the very short list of games I am willing to buy new, and I look forward to the next punishment eagerly.