OK so I played a good 5 or 6 hour session on Sunday in one game. I chose "Easy" difficulty because its the one that has no handicaps for either you or the AI so I assume it is equal to Prince difficulty in Civ games.
I am anti-RTFM so I just jumped in without reading about anything whatseover besides this thread and the guy's review on it. I was pleased to find the game is extremely intuitive and the UI is nicely streamlined, so it was no problem getting into the game and learning as I play.
It definitely does scream Civ 5 expansion to me due to the hex map, UI and general gameplay. One nice thing they didn't use from Civ 5 was you can stack multiple units on a single hex.
As I explored the world with my initial 'Warrior' unit I didn't really find the terrain very exotic or exciting besides the fungus tiles which don't allow you to build improvements on them and damage units moving through them but you can research techs to utilize them.
There are a good deal of 'barbarians' wandering the map though they are represented as native alien creatures and they range from little zerglike weaklings to big goliath land creatures and flying dragon things. You will not be able to kill most of these things until you develop stronger units. They are also all docile at first, I was a bit weary as I explored because the tooltip said it was dangerous but that's a bunch of bologne, I can end turns right next to the giant beasts with my tasty human treat units and they don't bother them. There is a certain timescale which can be modified as initial game setting which determines how long it takes before they turn violent and start attacking but I found that by the time they do I was able to field plenty of fire wielding units to handle them.
The unit customization is pretty cool and reminiscent of Alpha Centauri though not quite as in-depth as I remember SMAC being. It is a rock paper scissor system which I like where certain unit types excel at fighting certain other unit types. For this reason you want to roam the map with stacks that have mixed types in order to have the game choose the best defender when someone attacks you. There are bombardment type units though which can damage all units in a stack but it seems to be limited to just one type of artillery gun that has very limited application and I have not seen the AI use it. There is however this Orbital Bombardment building you can construct which has a 5 turn cooldown and when ready lets you bombard a tile in your LOS causing small damage to all units in that tile. The AI exploits this a lot and tends to build it in every city they have so it can get quite annoying facing this when you have stacks.
The AI is really good, I like how they combine forces intelligently and mount surprising attacks on you. Several times I have had cities off the front lines I left unprotected get captured (Cities dont have any of their own protection like Civ 5) which was a bit annoying because that means the AI doesnt need to have them in their LOS - they know right away if any of your cities are undefended and they will try to grab them by skirting around the front line.
The city development seems pretty solid there is a fair amount of specialization you can have in cities but unfortunately building everything is always good I dont really like that in Civ games. The way you utilize tile resources is not like Civ, instead you get a benefit from every tile within the city's influence which is 1 tile in each direction, which starts to grow after the city reaches size 8. Minerals seem to be the key resource because they feed production which consumes a lot of them, food on the other gand I always seemed to have in surplus without really giving much thought on it
I like the way resources are shared globally for food and minerals, this helps especially for expanding your empire because new cities you can put guys right into workers which use minerals from the global pool and give them great production capabilities quickly if your other cities have surplus minerals (each worker consumes minerals depending on what production bonuses you have from factories and sometimes special resources). Also for expanding they have a tech to boost growth so you can develop big new cities quickly once you have a good core empire.
All in all I had a lot of fun but already being burned out a bit by Civ 5 I already don't feel like starting a new game yet. I dominated my first game pretty easily by military conquest.
[Edit] Oh also I really should add that the game is stable and polished, I have not encountered any problems. And the AI turn goes so fast unlike Civ 5 where you can go make yourself a coffee while the AI takes their turn