So I finished a SP campaign with a win, played a total of ~10 hours, so here are some detailed impressions:
It's an RTS, but it's not so frenetically fast paced as to be a clicky mess. I like the speed of the game... I think it's really well done. There are definite... preferred build orders early on. I like letting power float for a few HQ levels and just accumulate some debt, get iron, aluminum, silicon, and steel/glass manufacturing at a good pace, with water and maybe a fuel/oxygen plant going. Obviously some maps will require different strategy, but it has worked fairly good for me.
The one issue I would say I have is it seems to be a race to the rockets. Once the rocket income starts coming in, it's just a matter of time. Hell, I normally intentionally crash the local markets for all products once I have rockets to insure victory - which just makes you more liquid than your competition and makes buying them out easier. I don't know if this is working as intended or a flaw, and can't really decide (trading offworld SHOULD be a huge money maker, after all).
The campaign needs some work. I like the format, but some more ability to customize, and some sort of signal for victory would be preferred [as it stands, when you eliminate the last corp you just go back to the screen]. The ability to customize the campaign, or play out some set ones, or have more corps/reactivity from corps would be cool. The other thing is in the campaign there are definite preferred missions to take. Generally, take the ones that give you free buildings - it's like a free claim. At the end of my campaign I had a free mine, free reactor, free solar panel, free glass workshop, free water pump, and a free chemical factory right from the jump, which just makes the last couple of missions too easy. I was playing on the Employee difficulty though, so maybe I just need to crank it up next time.
There doesn't seem to be much if any risk in just letting debt accrue except for the effect it has on your stock price, but generally I would say the benefit you get from the auctions for extra claims/tiles/perks far outweigh the debt problems. I've gone six figures into debt easily (normally happens when they EMP my solar panels when the price of energy is particularly high) and still not had a problem winning.
RE: Black Market. Eh - more often than not it seems like a waste of money to spend it on anything other than new claims. I mean, you can interrupt some supply or something, but I don't know if it would be enough of a hindrance to make it worth it.
Ultimately, this feels like a game that will shine more in MP. I haven't really played any MP yet, but will probably do so over these snowy days we're having. Maybe this is me, but for the life of me I can't fathom why anyone WOULDN'T take expansive as their HQ type. Otherwise you're just so damn limited in claims, so that may be balanced in some way. It's a really fun game though, and pretty unique. I can't recall playing anything quite like this before. Enjoyable experience - would recommend.