SC2 is utter crap, plain and simple. Chris Taylor strayed so far away from the SC/FA formula of old that SC2 is a totally different game altogether.
Experimentals have been butchered totally and split into Minor and Major Experimentals but even the latter ones are rubbish or overpowered. They're so poor that the DLC on steam now adds the Monkey Lord to the game just to tempt gamers to play.
The visuals are dreadful, completely dreadful. There is just no detail on the models at all vs the gorgeous models in SC/FA. If you zoom out of your base, you just see blobs of units, which are hard to make out. There just isn't any detail to the game if you look at SC/FA. Its sad.
Chris Taylor hired the AI chap who wrote the SorianAI mods for Forged Alliance to do the AI for SC2 except there isn't any full stop for Skirmish games. The AI doesn't probe your base, it just sends tons of air at you, followed by random land units.
The research system for the game is sound, as is the resource/mass gathering.
SP mode is ok, but as crap as it is in SC/FA overall. Not tried Multi as I couldn't even find anyone who wanted to play it back during release.
I did buy the DLC pack during the Christmas sales as it was about £3 or so because I was drunk (even bought the mafia dlc

) Not tried it yet though. Tbh, the game isn't even worth the space on your hard disk. Just get forged alliance instead.