5–30 mins (Mac OS):
Copied the app to a custom folder specifically made for games. During the first launch I was fast enough to make a tea: gui loading phase was long to wait at fresh install, plus cmd+tab doesn't work so I had to relaunch to copy the serial number.
I was expecting setting/plot to be deep and serious, so was dissapointed immediately with factions (childish portraits, silly description, everything is superficial). Hoped there would be more of them and that I'd be able to change names to my taste.
While reading about the red faction there was a moment when I hesitated to leave this game for good because of the liberal bias and cliche xenophobia. What was great about Alpha Centauri, among other things, that it was above and beyond nowadays morality and politics (true science fiction). You could easily settle in the ideology and concepts of any faction without being restricted to a specific moral alignment or judgement. Of course, at this point I did not realize yet there's no much setting or plot here to worry about.
In-game performance is very good (shame on those laggy Civ4/Civ5)! Visuals (terrain, units, aliens) are pleasant. However, my eyes were hurt at first by the contrast of white letters on dark background and I skipped a few tutorial messages and compendium events.
Interface and mechanics are familiar to me from all Civ games out there, I liked both as they are and the more I played the more I liked them. Especially: (1) accumulable resources, a nice alternative to the standard mechanics yet simple and balanced (comparing to similar Civ4 mods); (2) citizens management, much faster and less annoying than in standard Civ game; (3) the right side of the screen where you have smart button and events pool.
The thing I immediately hated about interface is that you can't see how many turns/steps it would take for a unit to move to an indicated position. Plus, sometimes the unit starts moving/attacking when mouse button is still pressed, I do not know if it is an issue of my mouse or the engine.
So that there was no need to struggle with gui nor with any annoying micro-management details, as it happens in Civ, I forgot about the lack of plot and was enthralled with pure gameplay for a few hours.
Hours and days (Mac and Windows):
My first game was going well but too calm. The reason was the size of the map. I changed it to Small (still with 6 opponents) and to Continents (to have less uncoverable landmass), and set alien aggression to High. I played all subsequent games with these settings and the green faction on Moderate level. I quit several games being overhelmed and two games because of inevitable crashes at a specific turn (Mac OS). Updating to 0.25.4 solved the crash problem on Mac OS.
I have Windows installed on the same machine (mac mini), so at some point I started to play under it. There were no inevitable crashes (the version with which I played is 0.25.5), but a pair of one-timers. Animation seemed to be a bit twitchy at first. Launching the app takes longer. All in all performance appears to be the same.
Regardless of being defeated several times I feel there's not enough competition in the game. In Civ/Alpha Centauri you have wonders, council, tech trade; alien life is more active, sudden and not that easily wiped out. I think I was not able to make an ally of someone a single time nor they do it among themselves, AIs are loners!
In the last game I won tech victory, specifically aiming for it. It is a pity there's no special tech or project you must reach to win that way, on the other hand the way it is fits overall simplistic style of the game. Talking of simplicity, it is good that there's still
strategy there (and enough of it, contrary to Civ5 where you "collect points" as if it is some kind of arcade or child-friendly RPG).
There were other flaws in the interface I stumbled upon: (1) messages about units been damaged by bombardment, dozens of them, (2) it's hard to notice the circle of an active unit when the unit is in a big city, (3) can't operate text fields via Enter, etc (have to use mouse). Considering #1, it would be reasonable to give only one message for all units
damaged in the same tile, while messages of destroyed units may come separately, as they are more important and less frequent to spam the pool.
It might be obvious but I have not realized the tech tree is random on my first two or three games. Actually I thought it is dull and unrealistic at first. When I finally got it, I loved it

, and the tier feature. Brilliant solution to replayability!
System played on:
Mac mini: Core 2 Duo 2.4GHz 64-bit, 2 GB RAM, NVIDIA GeForce 320M, 5200 rpm hard drive.
Mac OS Mountain Lion and Windows 7 (both on mac mini).
Screen resolution: 1920x1080.
P.S. I anticipate Pandora will be good in multiplayer.