This game is HUGE, just like Supreme Commander it requires an awesome PC to work, but it is worth of it! The game pace is faster than in SUPCOM, units are less expensive and take less time to build, moreover, they're faster! Battles everywhere on the map are common and the new Seraphim faction has been implemented really well.
BUT! Yes, but.... You can play the game smoothly only against 3 AIs. You will never be able to play a skirmish against more than 3 AIs or you will see a GREAT speed loss and the fame itself will seem to play in slow motion! TERRIBLE! This is due to some AI problem occuring when there are many units around, problems not present in SUPCOM, strange but true.
In short, when, AND IF (in their forum no one talks about a patch), GPG Games will patch the game you can buy it, otherwise I suggest you to buy SUPCOM.