I've watched the first few episodes of this on TV-links. Like the Shield, it's easy for n00bs to be put off by the whole "UNITED STATES MILITARY! HOO-HAH!!" bent of the characters and dialogue, but beneath this is a series that gets more compelling and it goes on.
David Mamet and Shawn Ryan produce it, so that pretty much guarantees that the dialogue and the action, respectively, are A grade throughout. The geezer who was President Palmer in 24 stars in this and is fantastic - even out-Bauering Jack himself in one scene.