I decided to wait a while before posting my hands-on to make sure that for one, I knew what I was talking about, and two, to see if any huge sweeping changes would hit the game that would drastically effect my opinion. So this might be a bit lengthy since I want to cover as much as possible about the game. Understand that I have played in Bronze and Gold league in 1v1 and Silver, Gold, and Platinum in 2v2. With well over 100 games played total.
Lets start with the basics, what is the same. The races, Protoss, Zerg, and Terran are still the only playable races and in many ways they still look, feel, and play just like their original counterparts. I will get into more detail on each race in a later hands-on.
Many units and buildings that everyone is familiar with still exist, the game still plays very similar to the original. Build some workers, mine some minerals and gas, build units, profit. These basics are where the "same" section ends and where the "different" section kicks in, because anyone who told you that this game is a re-skinned StarCraft, or Warcraft 3 in space, is a dirty liar.
Micromanagement(micro), manually controlling everything as much as possible to ensure maximum effectiveness, is still a huge part of StarCraft 2, and it has been made a lot easier in many ways. The waypoint system for buildings has seen a massive overhaul. You can waypoint workers right to minerals or gas, you can waypoint units into an enemy base and they move-attack to them. Hell, you can even waypoint units to a unit, so you can constantly reinforce your army as it roams the map.
Unit control is a lot easier with the increase in the amount of selectable units, no longer is it a bunch of control groups of 12 units since you can now select every unit you own in one sweep. On top of that, it is also easy to juggle multiple special abilities since you can just press tab and it will scroll through selecting all of one unit type at a time.
Ex. You have a zealot, a sentry, and a high templar and they are all selected. You can move-attack into an enemies base while watching the zealot to see his cooldown timer on charge, press tab and throw up a forcefield with your sentry, press tab and throw a psi-storm, and it takes a matter of a second or two to do all of it.
Also, skills themselves have a "queue" system for units which allows you immense control over your army and their special abilities. The way it works is, let's say for example you have 10 high templar selected. You click psi-storm, then click where you want it, and only one of your high temps will shoot his psi-storm, instead of all 10 of them. So assuming T is the shortcut for psi-storm, it would look like this to cast all 10.
T, click, T, click, T, click, T, click, T, click, T, click, T, click, T, click, T, click, T, click. Now I know it seems annoying to have to do that, but it allows you so much more control over your army without wasting the precious energy of your caster units.
Macromanagement(macro), this is your building and economy control, such as how good you are at spending your resources, and keeping your building production full. One of the most immediate changes that anyone will notice is the ability to select multiple buildings at a time, which makes building an army much much easier. A lot of the same selection changes from micro also are in effect here.
Lets say you have 3 gateways and want to build 3 zealots, you simply have all of the gateways selected and press the zealot button 3 times, the game intelligently assigns 1 zealot to each gateway. Also if you have a ton of buildings selected you can also tab through the building types while they are all selected. A large part of the new micro/macro play in this game is all about not only the new features themselves, but some interesting quirks to each race, which I will cover in their unique sections.
The last change that players will notice is the AI in general is so much smarter, no more need to pull a surround with your zerglings, the AI will do it for you. Also unit pathing is a lot smarter (although the new system does make units stack up a bit).
As strange as this might sound to the casual players, this is actually one of the biggest complaints about SC2 from some people. Many people feel that the need to manually control everything your army does, to maximize efficiency, was all part of the skill of the game. Now, I can't entirely agree with this sentiment and I want to express just for the sake of argument, that I am a Gold ranked 1v1 player and have even made Platinum in my 2v2 team, so I am an experienced player myself.
What I feel like they did with the AI is they simply took away the dumb annoying elements of unit control and allow you to concentrate on actual micro, not AI compensation. Anyone who thinks that they dumbed down unit control should watch a Marauder vs Zealot fight. See what happens to the player who micros his Marauders compared to the player who doesn't.
I am sure there are changes I am forgetting, there are so many to mention this article alone would be a 10-part article, but I figure those are most of the major changes. A lot of the little stuff most people know about, Xel-Naga towers, less vespene gas per trip, destructible rocks, etc. Those you can see easy enough, this is more a perspective of what you might know about but cant experience without being in beta.
Check out the rest of the hands-on articles within Starcraft 2:
The Old, and the New
Terran
Protoss
Zerg
Battle.net
StarCraft 2 Beta Review
