I've finally had enough free time to write this article, so here goes:
The game is definitely not done. The build that Blizzard is currently playing is nothing like the build we had here (supposedly); Zerg are changing almost everything every time we play it. On to specifics.
Lots of damage type changes, most of which I will detail later on.
New Vespene Gas mechanic. Two geysers per base, as we already know; these geysers only have ~300 on hand at a time. The geysers are deeper than that, but you're only allowed access to them for a minute or so. The geyser then enters a "rearming" phase where it turns red and your workers sit there unmoving. They do not give idle icons, so it's up to to player to micromanage them. Also, when the geyser comes back online it does not give a warning, so it's up to the player to put them back on. More on this in the audio segment.
Jackals (now called Hellions) are now Mineral-only; 100 for each.
Teching is totally diffrent now. +Attack and +Armor upgrades are now at the Tech Lab for the appropriate attached building. The Armory now contains all the pertinent Siege Mode, etc. upgrades; the Academy contains Stim Packs and so on. The Engineering Bay now has very unique upgrades: Additional Armor for Terran structures, and an upgrade that increases the range on Missile Turrets and the Planetary Fortress.
The Nomad was renamed and casts Spider Mines and stationary turrets. Mines are as good as ever from what I saw.
The Nullifier has this sweet new ability reminiscent of Chain Lightning. It deals 10 damage to 10 targets on the condition that they're the same unit as the first target. Think of it like a Zergling-only AoE spell. I suspsect 4-Nullifier drops may be fun to toy with. It costs 125 Energy which does take some time to accumulate, but it really makes a significant impact in the battle. It's available at a lower tech level than Psi Storm which is why I suspect it's so much weaker.
Dark Templar also merge into Archons. I think this was already known, but I made a point of reading the tooltip last weekend and Dark Templar make regular Archons. I guess you can make them less Gas-heavy now.
Psi Storm now deals 80 damage over 4 seconds. This is a good compromise to account for smart casting I think.
Observers do not require an Observatory, though this was mentioned by Blizzard before.
Warp Gates' (I believe) unit creation cooldown is now relative to the unit it makes, so they will always be more efficient than Gateways for every unit, not just a few.
Like I mentioned, Zerg are changing a lot every time. Both of the other races look to be getting close to finalized, with only a few tweaks; radical design changes are much less likely.
Banelings are Mineral-only units now; 50 minerals for two Zerglings, each can morph into a Baneling for 50 more minerals, so a total of 75. They are not cost-efficient at killing anything. More on this later.
Hydralisks are "normal" units now. In prior builds they were 100/100 Minerals/Gas. In this version they were either 25 or 50 Gas, making then a more accessable unit. In this build they behaved similar to regular Hydralisks, though apparently in Blizzard's most recent in-house build, they are a dedicated heavy anti-air unit.
Roaches are Mineral-only as well. They have bonus damage vs Light targets and I'll have more on these units later as well.
Nydus Network/Worms are different. Now you build a Nydus Network and load units into them, then you use an Overseer (upgraded Overlord) to spawn a Nydus Worm at a given location. Units then spill forth, etc.
The Defiler unit, whose name I really can't remember, is completely different from a regular defiler of course: It can move while burrowed, it "summons" Infested Marines, it has a 10-second Mind Control that I used to take my opponent's Mothership for about two minutes as I attacked his base, and it has a Broodling-esque spell that does damage over time, paralyzing the unit, causing it to explode when it dies.
Queens now cost Minerals and Gas and two food. I think they're no longer unique units, but I never made one.
This will come in part two along with an audio portion, or simply will be contained in the audio portion, which I may transcribe around the same time. We shall see...
Audio portion is up now! Download it HERE!!