Interesting, I just started playing this again in the last week. I found it surprisingly accessible after all this time. Especially the slightly pessimistic hard sci-fi content given the current political / environmental situation.

You can buy the game on gog.com relatively cheap, and there's a set of community patches for things like widescreen, better AI, and other features at (http://alphacentauri2.info).

The biggest annoyance I've found is moving multiple units. I think other civs have figured out grouping better. Alpha Centauri hasn't quite gotten this.

I definitely rank this in my Top 3 4X games (w/ Master of Orion II and Civ V)