I vote rental. I don't understand the popular culture of today's 20-year olds, but see no reason I should be able to understand it in 20-year-olds in the Army either. As long as they do their job, I wouldn't go complaining.
I had one chap attached to me I had pegged as a loudmouth immature arsehole. That said, he was a very solid guy when the shooting started, very dependable. An appreciation of rap off-duty doesn't mean he's a bad soldier, I guess, regardless of taste.
What I will caution about the movie is that it doesn't show what life is like in Iraq. It shows what life is like for a particular group of soldiers in a particular part of baghdad. Whilst I could see some similarities between what I went through and what I saw on the screen (particulalrly jokes about the locally armoured HMMWVs!), the movie just didn't 'take me back'. I had an entirely different war to these guys, simply by nature of my job, location and the fact that we were a reserve unit with an older average age.
NTM