I'm pretty hyped for the new melee animations, especially the new sounds, everything sounds really sharp in the Alpha.
Old stuff
Bladestorm could use some polish, it looks really aged next to the other new animations.
Avatar as well, it's supposed to make you look metallic, but you just look grey and slimey.
New stuff
Defensive Stance for Arms makes you equip the generic alliance/horde shield Spell Reflect uses, it would be neat to have a glyph like Weaponmaster to show a shield from your bag instead.
Ignore Pain for Prot is pretty underwhelming, you get a black skull over your head, I think it's the old Bloodrage effect?
Artifacts
Fury: It would be cool if killing blows sometimes made a Val'kyr descend to pick up the soul of whatever you killed. Would fit in with being Odyn's champion and wielding his weapons and stuff.
Prot: Grow horns, grow wings, cough up fire or somethng, wielding Deathwing's scale could have some side effects on you, make you a bit of a Drakonid. I guess that's what they're going for with the T19 armor, but something prot-specific would be cool.
Arms: Stromkar should whisper stuff to you, I loved how Xal'atoh did that, you could even have dialogue windows with conversations.
I'm not sure if it's been posted before but the new Heroic Leap looks
amazing