I agree with David. And, I have been playing Brad's OS X version of Alpha Centauri for the past week. Got a bit bored with Civ3 endgames. I do recommend the 'player1mod' available on the Firaxis website if you want a slightly different Civ experience. Battleships and bombers come into their own and the upgrade paths work for both me and the AI--less 'obsolete' units hanging around.
The Editor will allow me to 'tinker' and perhaps adjust some of the units, so that I can get my SAS troops into the endgame. I enjoy using the Privateer and would like the opportunity to use similar units in the Modern Age. The new patch from Firaxis looks great, so there is plenty to look forward to. And then, there's 'Galactic Battlegrounds' later in the year which may fill the SMAC/X void a little bit.