Played for maybe an hour or so. As some background I never got into Supreme Commander but like RTS games like Starcraft.
First off the UI, for an early access game, is pretty decent. It is a bit cluttered with stuff going on but it is easy to navigate and find stuff. I didn't care for it forcing me to make an account and log-in and have a separate friends list from Steam.
I haven't played MP so this is all from the SP "campaign."
Basically you start out with nothing. You have your commander and you build your basic stuff and you want to kill the other commander. As you jump around the galaxy you find various techs that you can socket. These techs basically unlock more of the tech tree. It is a nice concept but feels a bit restrictive. The way it seems you won't have the full tech tree at your disposal. But there are techs that you find that increase your tech deck. I think I'm at like 7 or 8 now. I've found techs to unlock advanced factory, nukes, sub-commanders (AI controlled ally faction), improved defenses and the like.
You "jump" from galaxy to galaxy somewhat akin to FTL. When you jump you either land on an empty galaxy you are free to "explore" to find tech [note: this happens automatically there isn't a Mass Effec-eque minigame or anything] or an enemy commander is in the galaxy and you fight. The difficulty of the commanders seems to scale based upon their color. It appears orange = super easy, red = easy, purple = medium. At least that is what I've found so far.
As for the gameplay it self it seems pretty stable and good. It is much more like Supreme Commander than Starcraft where you have absolute hordes of units you just toss at the enemy. I haven't encountered an AI that has really survived my initial rush. The economy of the game seems to be a teeter-totter you try and balance between Minerals (steel, I think) and Power. I haven't fully figured out how the economy works but basically you "pay-as-you-go" instead of Starcraft where you pay up front. So if something costs 15,000 Minerals (you can only bank like 1000 at a time) it will just be a drain on your mineral income. This is where the teeter-totter comes in. If you have a slow mineral income it will quickly drain your reserves and you need to halt construction on the building to get back enough minerals to continue. Power (which I have yet to figure out exactly how it is drained and at what rate) measures your effeciency. So if you lack power to construct something it will construct at 25% the rate. But if you have +500 mineral income and the stucture costs you -200 minerals per cycle you will still net +300. So you can build more shit. But if you try and build 5 things at once chances are you don't have the mineral efficiency to do that. So you'll try and make 5 things at once which will take 1000x longer than just making them one after another. Generally I have three "teams" making stuff. I have yet to really figure out the ratio of extractors
ower plants:factories.
Overall I think the game has potential. I haven't really gone into different planets or launched nukes yet.