Unfair, but that's your basic plot. Put upon young kid gets hassle, enters competition with hasslers, triumphs.
End of the day though, it's a very good flick for lotsa reasons. First, if you like Eminem, you'll like the movie, because there's a lot of him in it, doing his thing. He can act, in as much as he can play himself, and that's what he does. Not sure I'd cast him as Hamlet or anything, but he does a good job.
Plot wise, though it's nothing new, it is new because it doesn't have a cliched, uber-happy, "everything's going to be alright now" ending. The story seems pretty realistic, since nothing unlikely happens in it at all. No huge record contracts from mysterious talent scouts appear at the end, and so you can sit back and watch, safe in the knowledge that no "Yadda-yadda" clichés are coming your way.
And that's another thing about it. It all seems pretty real (for all I know of 90's Detroit). There's black guys, but they're not all in gangs and waving guns. Two guns appear in this movie. Two bullets are fired, only one hits anyone. This isn't about violence, it's about a realistic view of grinding poverty, and people trying to get out of it, or at least exist in it.
Bad points? Not a lot happens. Which is fair enough, since it's a film about little people with big problems which aren't going to be solved in 90 minutes. But does leave you feeling a bit like nothing much happened.
Still, it's a "didn't look at my watch" movie, and one which I would recommend on a "If you're in the mood to watch a film, go see this one basis." Don't make a special effort, but I think it's probably the best thing in the cinema right now.
I'll give it a solid 8/10, and you might give it another one, if you were a big fan of Eminem, and would get a big kick out of watching him rap.