Just finished the Diablo 3 beta. Holy crap it's awesome. So much ass kickery that I can't take it. I actually got pissed when the beta ended it's so good.
The best way I can explain it is it's like Blizzard went into a coma for ten years right after they finished Diablo 2 and then woke up with all this new gaming technology and made another one. Everything you liked about the original Diablos is there and unchanged, and the things you didn't like have been changed.
Looting is so easy now. You have these "scrolls of companions" that last about ten minutes a piece, but they drop literally every two minutes. You get these random little animals like snakes, scorpions, spiders, ferrets, pigs, etc. and every time gold drops they scoop it up for you automatically. They don't loot the gear so you can see what dropped and decide whether to leave it or take it.
You also meet companions along your journey and you can ask them to join you (NOT HIRING THEM, BTW...YOU DON'T HAVE TO PAY THEM). It's kinda like the SWTOR companion system. Best of all, THEY FUCKING DO WHAT THEY'RE SUPPOSED TO DO. They kick just as much ass as you do and often will talk to you and you'll even respond to them, all the while slaying hordes of monsters. There's literally zero break in gameplay during all of this. No fucking choices, no fucking worrying about character development; get your gear, sell your gear, kill more monsters and further the storyline.
They've also added a function where you can scrap your garbage loot into things you can use for crafting...yes, CRAFTING. You can craft weapons, armor, etc. The leveling system is kinda cool, albeit a bit different. The higher levels you get, you don't just get new abilities, you get the privileges to use them. You have to earn the ability to equip more than two spells at a time, and this is done in the lower levels, like from 1-20. I actually like this because it gives you smaller goals to work towards instead of just trying to level up as fast as you can so you can go kill X.
I haven't seen the ability to add skill points or anything; I don't know if it's just because it's the beta or that they decided to scrap that altogether and just distribute them automatically. However, you now have passive abilities too, WHICH FUCKING RULE. Shit like, "Every time you use arcane magic, you slow them by 25%" and stuff like that.
I'd say my favorite feature is the health baubles that drop. There still are the health potions just like always, but they're kinda separate. After killing baddies, health baubles will drop and you just run over them and they heal you, effectively doing away with the spamming of your quickslots in hard fights just to stay alive. Those quickslots, while you can still use them for health potions, are free to use for abilities. Didn't see a single magic potion. Your mana automatically recharges and a quick rate and certain abilities/spells take more than others. You're given "class abilities" like magic missile and others for the wizard which don't use any mana at all, thereby freeing you to use your mana for the heavier spells and more destructive abilities.
All in all, I'd say the UI has been incredibly streamlined in favor of the gamer and this is the best part of the gameplay, imo. No more adjusting your loot, picking up tons of potions, etc. Everything's there and ordered for you. All you have to do is go rape everyone in the face and then take their shit. This game is so FAST. There's no downtime except for going back to sell your shit and pick up more quests if you need to. It's 0-100 mph from the outset and it doesn't let up. It's a hack n' slash on the most potent of steroids.