A pal of mine let me in on his beta key for Diablo 3, so I played it. And played it. And played it. And...
STORY:
As for the story, it's hard to say entirely since the beta only lets you play through the first chapter. In the first chapter alone, there's a lot of interesting cogs being set in motion, each set up in ways that the player can visually see unfold as he progresses on his journey. This was a big problem I had with the previous Diablo games (Diablo II at least made an occasional attempt), and Torchlight. For one of many examples, in D3 there's a quest where you have to help a blacksmith kill a group of zombie-infected villagers... along with his wife. It is a small part in the game, but it set the tone for the game very effectively, and got the player personally involved in what the village was going through instead of relying on a "Talk" button to find out.
Another nice touch I enjoyed were the bits of lore they left lying around for you. When you kill a new monster, a "New Lore" button will pop up at the bottom right of your screen, and with a single click, an audio clip begins to play as someone's journal narrates the creature's story. This will be stored separately in your journal if you feel like revisiting it. Tomes like this will also drop off bookshelves that will give deeper insight into the current quest you're playing through. So while they have all these little tomes and pushing "Talk" on the villagers can give you deeper understanding of the story, you won't be lost if you don't do it. They properly place events throughout so even if you just bum rush through, you know why you're doing it.
GAMEPLAY:
HUGE improvements that take definite high roads from Diablo II and other games in the genre.
1. F***in' potions: constantly ruining the other games for me, the potions had the potential to destroy the flow of an entire game. Why? Everything was designed to be fighting a potion-chugging warrior that has to portal back every once in awhile to fill back up on his fix. And then one guy in the crew says: "You know what would be cool? Doubling the potions. Make them need it for mana too!" No longer my friends. There are potions, but they are instant, and on quite a healthy cool down. Also, each character has a different "mana" system, none of which require potions.
2: Town portal and identify scrolls: oh my hatred for these two objects. Yeah yeah, go back to town, fill them up, take the trash out, do laundry, pick up the kids, do this year's taxes, file the paperwork... that's how fun I felt it was. Town portal scrolls are gone altogether and have been replaced by a "hearthstone" that doesn't take up inventory slots, and has a cast time, so no more cheesy escaping while Diablo's running you down. As for identify scrolls, don't worry, they've still kept the "ooooh what did I get what did I get?!" factor, but it isn't for EVERY SINGLE DAMN MAGIC ITEM YOU EVER PICK UP. It's for yellow or above items only.
3. Character Customization: YES! The points system is GONE! I know I know. Gamers love points systems, we do. But fact is, they're counterproductive to the purpose they were originally meant to serve, which is why they're getting rid of it in World of Warcraft as well. They were designed to let the player build their character toward their own personal gameplay style. They serve the opposite purpose of pidgeon holing people into a given set of a gameplay styles, and if they don't build just right, that build is not the "optimum" build. There is still a great deal of character customization however. Being able to use any of the moves as you level up, they will level up along with you. As you level, you will have more action slots available to be able to use more and more abilities at a time. To switch these abilities out, all you need to do is go back to town and touch a stone that will allow you to swap any of your abilities out. There will be runes as well, but I haven't gotten to those yet.
4. Graphics: The subtle use of the physics engine is amazing, and particularly fun if you're beating people to death with the Barbarian. It's not overused to the point of silliness, and that separates the pros from the n00bs in game design. The models of the characters are made efficiently by masterful 3D artists, leaving virtually no extra or unnecessary polygons, for both maximum performance and style. The animations are fluid and fun to watch, and even the most insignificant monsters had some serious time put into animating them properly for numerous possibilities. The simple act of beating mobs to death in itself, or even breaking pots, is richly rewarding due to visual reward.
5. Crafting: You know all those white or gray items you used to grumble at and walk right over (quick note: they don't take up half your inventory anymore)? They're quite useful now. Any equipment you pick up can be converted into crafting materials for your new set of rockin' armor, or your sweet new axe. I now find myself greedily snagging anything that I can pick up, and gleefully converting it into raw materials for my new set of gear. Also, as your blacksmith improves (with pages you find and... ah whatever not important) so too will even your most basics sets of gear, as well as learning more advanced sets.
"But Jorumn--"
"Yes inferior member of the forum?"
"--what is the point in the blacksmith improving the basic sets if he comes out with advanced sets of gear?"
"Allow me to enlighten you, insect!"
6. THE STASH!: All of your characters now have a shared stash, and it rocks. Ever picked up legendary piece of gear off the Lord of Terror himself and said to yourself, "F*** ME!!! If only my necro was here!" No longer an issue. Your characters also share crafting NPCs, so if one levels up the blacksmith, every single character you have enjoys the benefits of a rockin' badass blacksmith.
"But Jorumn--"
"Ugh, f***in'... WHAT?!"
"If anybody can use anything for their alt characters, won't their be ninja looting issues?"
"That would be true, if there wasn't..."
7. SEPARATE LOOT: Everybody will get separate loot that benefits them. So yeah. F*** you ninjas.
I feel I've written enough on this for now. Suffice it to say that when this game releases... I'm gone.