Particularly because Samhaine is writing his system review of Spirit of the Century right now, I'm going to pull together as many thoughts as I can about my experience playing in the sessions he ran. My character was Max Gable, lesser-known twin brother of This Guy.
Max was particularly skilled in fisticuffs, gambling, and piloting. He was pretty much taken straight out of the rulebook, to be honest. I even had one of these (or maybe it was more like this) that the GM came up with a reason for me to use in each session. Actually, the plane had an almost completely undescribed artifact that let it do occasionally impossible things, like go on autopilot. I understand that the GM had Nefarious Plans for that undescribed artifact that never came out because the game didn't continue. Naturally, I also wrote several of my Aspects to be references to the guy in the picture.
But the most important thing about Max was that Max had a nemesis: Der Totenengel. Max's player is noted for not really knowing any German, so if the translation for the Angel of Death is wrong, I don't really care. What I did care about was that "Curse you, Der Totenengel!" is a pretty awesome thing to scream at the heavens when your nemesis has screwed you over or evaded your just retribution once again. Notably, I thought I was getting a nemesis about like this, but wound up with something more like this (disputably NSFW) in an excellent reveal during the final session. This is what we call "trading up."
Faced with twice as many interested players as he could ever reasonably include in one game, the GM set up a roster of twelve players, and ran sessions for various arrangements of six players at a time. This worked out really very well, as much of the interesting dialogue of each session came from exploring how these characters fit together each time. It managed not to feel like a "first session" each time, though, because we were hip-deep in action before we'd even finished introductions.
The locations of major encounters were excellent examples of the wahoo! action I had been led to expect from SotC. When you get right down to it, that feel wouldn't be my first choice in playing or running games; gritty fantasy of a medieval or modern character is more my speed. I loved this, though. We fought bad guys inside and around an airship (one fine example of a chance to use my plane), we fought bad guys on a double-decker bus, and we did it all at breakneck speed. (One of the other characters that I never got to team up with had the Unsafe At Any Speed stunt...) We fought bad guys on the docks, working our way through a maze of crates while they did something nefarious that I don't exactly recall on a docked boat. (This was when I discovered just how unstoppable my maxed-out Fists skill and a couple of steadily relevant Aspects really were in the face of what I can only call an onrushing horde.
So the game was pretty much a thrill a minute, but it never felt all that dangerous. As Samhaine points out, this does have a lot to do with the game giving you ten Aspects and ten Fate points and a pile of Stunts. In theory, the game makes you this powerful because you don't really ever increase in power. (Coincidentally, this feeds into Samhaine's othercurrent series of posts.) The game intends for players to create characters on a moment's notice, drop in to play for an evening, and have as much fun at that session (at least in terms of character power) as a player who has played the same character for years. I can't really hate that goal, but I do love watching my character grow in power - a taste not well suited to SotC, to the best of my knowledge. For me, that means that SotC is fun, but would have a hard time becoming anything more than short-term diversion. The GM did some great things to counter this, as I was pretty intrigued with the mysteries that he worked into the game, particularly when my character's mysteries were connected to another character's mysteries. Clues leading to solid discoveries are enough to make me feel like actual progress occurred. At some point in the future, I may comment on experience points and other progression models here, if only to avoid a thousand-word reply in Samhaine's comments.
Another thing that I really, really liked about the game was that scholarly types still had useful things to do in combat, making declarations about enemies and their capabilities to assign Aspects to them. These always ran the risk of getting repetitive, but we had some clever players and it mostly stayed cool. These chiefly had the effect of giving me (as the fighter-type receiving assistance) something good to spend a Fate point on later that round, or on my turn the following round.
I recall having some difficulties with the dogfighting rules. Well, okay, the GM had some problems; I didn't have enough of a challenge, if I recall correctly. I got out to an early lead thanks to some Spin, and there was just no way the enemy plane (flown, of course, by Der Totenengel!) could counter that advantage and pose a serious threat to me. I don't remember the rules well enough to explain exactly why this came to pass, but I'd written some Aspects to really help with that situation (since Piloting was only a +3 skill for me, despite being pretty important to the character's concept).
My conclusion, in super-brief, is that I would happily play SotC again, but ideally lowering the power level a bit. I seriously doubt that I would want to run SotC, because frankly I'm intimidated by how much work the GM put into the sessions I played. The NPCs had a web of connections and secrets that we had to unravel in pretty short order - it's the kind of thing that takes me a long time to write and an even longer time to reveal in a game. I do want to pick up my own copy of the rulebook for the sake of reading the advice to GMs. Who knows, I might also discover that it's less intimidating when I've read everything.