My beta play has been slowed down by the mind-numbingness that is being asked to chair a search committee at work, and Diablo 3 will probably occupy my attention for a bit. I'm a Loque'nahak kill from having finished Northern Exposure (Outland rares are being sneakier), and I've made back about 60k of what I spend on Poseidus (and then went and did Haris Pilton's bag achievement, and got a Kirin Tor ring, which was immensely handy). I may break down and get a Traveler's Tundra Mammoth with account-wide mounts going in, because, let's face it, I can't be an engineer on every toon. (Mostly due to the ore costs, really.)
So yeah, I've been in tying-up-loose-ends mode in WoW, and D3 isn't going to really change that. What D3 does have me doing is thinking about the evolution in the complexity in game play in both the Diablo and the WoW worlds.
I mostly played a Rogue in Diablo. I like playing an archer/ranged class, and you could still learn all the spells if you put enough points into magic. I put a lot of points into magic. Fire Wall was my go-to spell for practically everything, and I used Town Portal for extra light. Yes, extra light. I had the gamma turned all the way up, and I still needed more light. The game was pretty simple: you just descend through increasingly lower levels of the dungeon.
Diablo 2, and its expansion, upped both the complexity of the story and the game play: you could enhance items with sockets via gems and runes; each class had unique skill sets and talents (rather than everyone learning the same magic spells); charms could further improve your character; and the game had a distinct storyline that wasn't just "get to the bottom of the dungeon and kill the big demon." There was some flexibility (I had a stupidly huge amount of fun with a Barbarian dual-wielding throwing knives), and I could get away with things like stacking light radius or Charged Bolt procs on my armor. (35%+ chance of Charged Bolt proc was a delicious, wonderful thing.) I played several of the classes (Amazon, Mage, Assassin, Barbarian) that I immediately recognized the influence of when I moved on to WoW down the road.
So now we're looking at Diablo 3, and it's interesting to see just how much the evolution of WoW is influencing it in the same way D2 influenced the classes in WoW. You can glyph skills to change their utility, and the quests and lore have been much more fleshed out. The gameplay is a bit more... strategic? Some skill sets work better for groups, some for single-target, and I've found myself basically trapping and disengaging with my demon hunter to kite bosses or groups around, much in the way I would with my WoW hunter.
Still can't rotate the camera, but I'd imagine that decreases the overall video/data load of the game by having a flat, if animated, canvas to work with. Going back and forth between D3 and WoW (where I use click to move) is always an adjustment, as well. (One of these days I'll give in and invert my D3 mouse buttons.) I had to remap a lot of the default keybindings, as well, since I am a diehard qwasde user for in-combat movement.
Battletags were a nice addition, and through some experimenting with someone who had RealID disabled, but who I'd friended in D3 via battletag, we discovered that you can see someone you have battletag friended in WoW (that they're online, and what server they're on), but you can't see what character they're on, and you can't interact with them via the battletag/RealID communication or party invitation channels. Also apparently it will tell people when I am in both WoW and D3. Ahem.
Bottom line: I want Hungering Arrow in WoW. >.>