A lot of people (specifically, Fallout fans) were disappointed by this game, as the premise is somewhat misleading. Fallout Tactics isn't another Fallout game. It's not Fallout 3, and it doesn't have anything to do with the first or seconds' stories. While it does in fact use Fallout's S.P.E.C.I.A.L. character system, this and the game world are all this game has in common with the originals.
This might sound kind of silly. After all, sharing an entire game universe, in theory, would probably mean they share a lot in common: but the gameplay in these two games are totally different. In Fallouts one and two, you were a lone badass sent off on your own to explore the post-nuclear wasteland. Along the way, you might have picked up a few other stray co-badasses, but ultimately you were only responsible for yourself.
Fallout Tactics, on the other hand, will appeal more to fans of strategy games than RPGs (X-Com comes to mind). You have to manage a squad of up to 6 characters in either a turn-based or a modified, pseudo-real-time mode.
Perhaps the biggest change, to me, is the story style; instead of the free, open-ended world in the originals, Fallout Tactics is a completely linear, mission-based game. This is what turned me off from the game. Fallout 1 & 2's charm was that you could go pretty much anywhere at any time, and play your character however you wanted to. While Fallout Tactics does present different ways of solving a good number of the given missions, it's lacking the pure number of options that the previous games had. Don't expect to become a Porn Star, Professional Boxer/Prizefighter or a Slaver in Fallout Tactics.
Bottom Line: Don't buy Fallout Tactics just because you liked the first two games. It isn't Fallout 3, or even Fallout 2.5. It's a completely different type of game that simply takes place in the same game world. If you like Strategy games like X-Com and other squad-based tactical games, go for it. If that's not your thing, then wait for Fallout 3 (Whenever that's coming).