Well I like it, but then I don't have normal CIV2. I find the extra scenarios (fantasy and sci-fi) to be interesting spin-offs from the main game. OK, so I could probably buy better fantasy and sci-fi games, but I like being able to use the basic civ gameplay with different units, tech trees and settings. It keeps me interested in the game. Also, if you are playing the basic game in TOT, you can actually land on and settle Alpha Centauri, rather than have the game end. Again, this adds an interesting new dimension to it.
As to whether it is worth it, that depends on how much it is going to cost you. My copy of TOT only cost £10, which I thought was fine (even if the manual came as a pdf)
