If you still play the original Supreme Commander and/or Forged Alliance on GPG, then my advice to you is to keep playing. Forget that a sequel was ever in the works. Put your wallet away this time.
I've played Supreme Commander 2 for the past 2 days straight, and my verdict is this: It's an absolute and utter betrayal of everybody who stayed on GPG and played Supreme Commander and Forged Alliance up to now, in order to appeal to those who left GPG over the years because the game was too complex, too nuanced and too strategic for their modest abilities to cope with.
Even the largest maps are tiny, and massive armies can be conjured in just a few minutes. No longer can a few stealthed task forces strike like lightning at numerous key targets- some divided by oceans and mountain ranges- to weaken a dominant team's hold on a massive landscape and give your side a glimmer of hope(!). Instead, you build your tank stomp, they build their tank stomp, and the miniscule arena necessitates a head on attack every time. There are *no* strategies or tactics beyond this.
I'm not going to go on, this game is such a disappointment that I can't even summon a good rage. In summary, it's an unfortunate and troubling RTS effort. Gameplay is retro-RTS with none of Starcraft's precision or C&C's charm. Supreme Commander 2 is likely to trade well, all thanks to its predecessor, despite the many overwhelming and impassable shortcomings. Just save your money. Really, really, save your money...