Sanaa Lathan plays Sidney, an editor at XXL magazine who's been in love with hiphop ever since she saw Dana Dane and Doug E. Fresh battling on a street corner when she was a kid. Magically, that very same day, she met her best friend, Dre (Taye Diggs). Dre plays a big time record executive at Millenium Records, and he is on fire--wealthy, powerful, and about to marry this super-hot model-type lady. Even still, it's he and Sidney that share the real-love magic, but they've never been more than friends, although they are clearly meant to be together.
But, of course, Dre marries the model, and Sidney starts dating this basketball player/rapper who has all the smoothest moves, but doesn't even read her writing! Whatever! Of course, Dre has everything she's ever written memorized. He starts to realize their more-than-friends connection when he quits his job as major-label ho to start his own, independent label (so he can put out the album made by Mos Def's character).
So yeah, it's a sorta cheesy love story--if you're a romantic, you'll be charmed, and if you're not, the characters are just fine. (Also, Mos Def is actually a really good actor!?) But damned if Brown Sugar doesn't make the analogy between the crappy lovers and the crappy, poser rappers. One line even goes, "The difference between rap and hiphop is like the difference between loving someone, and being in love; rap is just a word." The state of hiphop (as a lifestyle) vs. rap (as a commercial interest) is the true story of Brown Sugar, and there's much dialogue to back it up. (There are also a lot of jokes for the music nerds, like when Mos Def asks Dre if he quit his job because the label president hung him by his feet outside a window.)
And, even if you hate Brown Sugar, it's worth seeing the opening scene: a documentary-style first ten minutes of Common, De La Soul, Slick Rick, Talib Kweli, Russell Simmons, and more, answering the question, "When did you first fall in love with hiphop?" Incredible.