Wow, I loved this game. I didn't expect to; my expectation going in to it was that it would be overly complicated and simulation-y. But it is neither. Sure, it's got complication, but all the complication seems to be DOING something; it's not just there for bragging rights.
It's three hours long, so it probably won't ever be a top game for me simply because I would so rarely be able to play it. However, of all the multi-player long games I know of (Twilight Imperium, Game of Thrones, etc.), this one is the best. I really, really, enjoy this game, even though my brain hurts and it frustrates me no end.
This is a game where every choice you make seems to make a big difference. Simpler than Puerto Rico or Louis XIV, both of which it feels a bit like while playing, and with less player confrontration than in either of those games. It also plays FAST, once you get the hang of it. Plays well at any number of players.
I've decided I like it more than Dominion, but in a different way. Dominion is faster, and more analytical; the goal is simple. Thunderstone plays out in stages and thus feels deeper, even though it might not be. I've already purchased three expansions and counting.
I can see why this game has ended up as the top wargame. Game play-wise, it is very elegant and smooth, with all kinds of tough, tough choices. Theme-wise, you really feel like you are seeing the Cold War unfold on the table in front of you.