One of the best TBSs ever...
For me, Alpha Centauri was similarly addictive and entertaining. It's probably the only TBS that actually has a plot, and an interesting one to boot (although it only crops up in brief sections triggered by in-game events, and you only see it through if you complete the game in the most difficult way possible). Furthermore, the concept of the Planet being almost a player in and of itself, which you ally with through tech advances, governing choices and terraforming, is incredibly interesting and makes the gameplay that much richer.
Of course, the basics are still there, and in some ways you can still see the grinding mechanics of Civ 2 underneath. Think about the fact that you begin limited solely to land forces, and gain the ability to create aircraft much later - given that this is supposed to be some time in the 23rd century or so, wouldn't they be using airborne units right away? There are some design flaws like this which only really grow to be disturbing after a long time playing the game, and it has a tendency to make up for it in other ways (for instance, if futuristic tech is your thing, wait till you see the top of the tech tree!).
Ultimately, SMAC is a very gratifying and entertaining experience, absorbing and very well executed. The production values are through the roof, and the gameplay is perfectly calibrated so as to be fun but challenging. If you consider yourself a fan of Turn-Based strategy games, you owe it to yourself to pluck a copy out of the bargain bin and play it for yourself.