Took them long enough to add a Hydra speed upgrade, but at least they finally did. I think it speaks for itself when the crowd at BlizzCon was the most hyped about this change (even slightly more hyped than about Baneling burrow move).
Most of these stuff will inevitably get nerfed to death or completely changed until retail (which is still way too far away), but in its current state, Viper seems to be the most interesting (but also admittedly an imbalanced) unit.
Dark Swarm, although its AoE isn't the biggest, but together with Baneling burrow move, is going to be ridiculous. Also Dark Swarm + Swarm Guardians against Blink Stalkers. And fast Hydras + Meat Hooking any Colossi / Templars next to them. Also if Ocular Parasite can give detection to massive units as well, then good luck killing a detector Ultralisk. Burrow charge will actually make them much more viable. (I know Ultras are actually used fairly frequently these days, hell even at BlizzCon just now, but still).
Swarm Hosts do seem like a poor man's Lurker; the attack cooldown is long, the "summons" are rather weak, and it's currently on Hive tech as I understood. I don't see why someone wouldn't just either rather go for Baneling burrow move or Ultras or Swarm Guardians instead at that tech level?? I wish they rather just added Lurkers back onto Lair tech, with a +3 range upgrade at tier 3.
Oracles aren't cost-effective.
And so instead of giving HT Feedback the same range as Ghost EMP, they added Replicators to copy Ghosts with Cloak researched and EMP the opponent Ghosts.
The Tempest is a "1a" unit that requires less micro than the Carrier that it's replacing (although Carriers were worse than their BW counterparts to begin with, which is what they should've rather tried fixing than removing the Carrier due to it being "too weak", despite the fact that White-Ra, Socke, etc. have actually used it with some decent success).
But the Nexus Recall might be the biggest change for Protoss. They better balance that properly if they intend to keep it.
And hey let's remove the Mothership because apparently hero type units don't really work well in SC2. Then let's make the Thor a hero type unit because maybe they do work out after all!
Shredders for stationary defense? Yeah right, Terrans don't already have Tanks, PFs, Bunkers and PDDs.
The BC speed boost ability with the cooldown is really nice though.
Not sure how to feel about Battle Hellions and Warhounds.
tl;dr overall some very cool changes (Hydra speed upgrade, Baneling burrow move, Vipers, Ultra burrow charge, BC speed reactor) and some very lackluster ones.