Well I recently got a chance to play this game in single player mode, I must say this game is truly amazing. While the Multi-Player looks very similar to the way the old SC did the single player game play is very very different.
The key elements are there, you build a base, gather resources, deploy forces. Where the game differs is in how the cut scenes look and the overall game play in between missions. You are usually in a room where you can navigate to different sections and do things like upgrade units, research new technology and so on.
The video below shows some of the new game play mechanics. That video is a bit dated and a few things have changed, for example the Thor is smaller and made at the factory and no longer built in the field as it was in this video
For example if you find enough Protoss research points you can easily buy an upgrade that lets your Vespian Gas refinery automatically harvest without needing a SCV to do it, this leaves them for more important things like building supply depots and harvesting minerals. Another cool one on the Zerg research side is the ability to have your buildings and metal units (Thor, Vulture and so on) heal themselves SLOWLY over time.
There is a small spurt in the game where you can play as the Protoss for a short time but I am not going to say just where so it is not spoiled for you 🙂
World of Warcraft and RealID
Recently a few major patches back Blizzard introduced a feature called RealID which until recently surved no real purpose other then to prepare for Starcract 2 (it also supports it). Now you can add a user using their RealID and you can then talk to them from ethier game and also from Diablo3 when it is released.
I tested this feature out and it proves to be a very reliable feature, there are a few issues for example if someone sends you a message right before you trigger a cut scene in SC2 then it stays up on the screen the entire Cut Scene unless it is one of the few cut scenes that require separate loading. You can not chat during a cut scene so there is no way to get rid of it.
This of course can work in reverse with people you meet on SC2 being able to talk o them inside WoW, I am assuming this will have similar function in Diablo 3