Dang, looks like there have been a bunch of advance screenings for this movie (just now seeing this thread for the first time).
I too caught an advance screening of this (quite fortuitously I might add). The trailers I'd seen before definitely sold the movie short, and didn't really accurately convey the movie either.
I didn't realize the movie was rated R until the over-the-top violence kicked in within the first 10 minutes.

Body parts got sliced off, people got impaled, and heads exploded! None of it was especially bloody though, not like a Quentin Tarantino film at least, just brutally violent yet graphic enough to get the point across without overdoing it with gore.
Probably the most defining aspect of the movie was its quirky yet accessible sense of humor throughout, with plenty of hilarious lines by all of the key actors - Colin Firth, Samuel Jackson (who had the most scene-stealing lines, as expected), Mark Strong, and the young guy who played the lead.
The mostly college-aged audience that I saw the movie with (the screening was at a local university) seemed to love it, there were tons of laughs at all of the comedic parts, and people cheered whenever a bad guy (there was more than just the major "villain" in the movie) got his comeuppance. I definitely recommend seeing this movie with a packed crowd.
Gotta say that anyone who doubts Colin Firth can do action should see this movie. He convincingly kicked ass and took names! The action overall was some of the most stylish & kinetic stuff that I've seen in a long time (surpassing anything that was in Kill Bill since that's the first movie that I can think of that most closely resembles its style of action), and there were tons of really-cool camera angles and equally cool stunts that had my audience either cheering or oohing/aahing.
Overall an amazingly entertaining movie that was admittedly campy but a ton of fun to watch with plenty of hilarious lines, tons of kinetic action, and protagonists to root for.
And I wouldn't be surprised if the lead young guy is cast as James Bond when he's older, maybe in about 10-15 years or so when he looks more rugged around the corners. He had just the right kind of charm & smugness that I expect from someone who plays James Bond, and I suspect he'd nail the character.
If all these advance screenings are expected to help with word of mouth, then all I can say is go see it when it comes out! I just saw it for free tonight but will probably pay money to go see it again on opening day!