Javaman and I dived basically blind into Supreme Commander vs the easiest AI in a 2v1 fight. We won a long and glorious game that consisted basically of that dog in a lab coat going "I have no idea what I'm doing". We never did figure out how to upgrade commanders past tech level 1. I had upgraded factories and engineers and so forth, but never got past it. We also both suddenly ran out of mass near the end of the game, so I guess you have to upgrade mass extractors earlier.
It seems like a cool game, but microing units seems rather difficult so I'm guessing you're supposed to just send waves into battle and let them fend for themselves. For instance, there's a mobile shield unit, but surroundings units in the command group tend to drive themselves in vaguely random directions instead of staying inside the shield.
I can only imagine how complex the game could become if you had lots of factories, big armies, and a map larger than 5x5 km.