Spirit of the Century is made of pure awesome, I've had more fun playing with it than any other game bar none. What's really great is that you can build the way that you role play into the mechanics (by making all of your RPed quirks Aspects) so that instead of choosing to do the tactically sensible thing and succeed or do the role played thing and probably fail, you just tap the right aspect and MAKE the awesome role played thing also be the tactically sensible thing.
Basically if takes the roleplayer/rollplayer distinction and tears it to shreds.
The only thing I'd change it make it easier to characters to get hurt, as things stand now its too hard to put them in serious danger without a long long fight.