I'm one of about a dozen people, apparently, who didn't particularly care for Sin City. 300 is another adaptation of a graphic novel by the same author, done in a very similar style.
The problems that plagued the first movie centered around dialogue; what works in a comic book sounds ridiculous on screen. It's possible, I guess, to ignore this and to just enjoy the movie as a comic book come to life. I couldn't quite make that jump during Sin City, but with 300 it's easier to do.
The character development is selective (aside from a handful of people, there is no effort at all at it, which works fine), but more effective than in the last movie. The movie itself centers around the famous battle at
Thermopylae in 480 BC. The outcome of the battle is never in doubt for the viewer. There is much testosterone-soaked chest thumping about honor, and some speeches about freedom which seem oddly out of place in a society where boys are taken from their families at seven years old and subjected to some pretty brutal military training.
There's also an interesting subplot involving whether the king has authority to fight a war without the authorization of the council, with various nefarious plottings to undermine his efforts. Different people will find that this resonates with their opinions on a different war, well, differently, but as the movie follows the graphic novel very closely and the graphic novel predates the war we find ourselves embroiled in, it's hard to say whether that's intentional or not. Of course, if I was making a pro-war movie in Hollywood these days, I'd deny it too.
Overall, worth a watch, and even the price of admission at the theater. Not terribly accurate on weapons and tactics or anything else, but if you walk in expecting to watch a movie based on a comic book based on a movie based on historical events, then you will get exactly what you want.
Oh, and there's nudity. Hooray for nudity.
But it was an EXCELLENT movie for guys, even better on the IMAX. 
