It's definitely useful outside of the noir genre. One use for it that I'm hoping to follow through with in the next couple of months is to run a LOST-style game where the focus is more on the emotional, social, and mental drives of the characters and less on standard game stats. If you've a chance, pick up Monsters and Other Childish Things and the supplement Dreadful Secrets of Candlewick Manor, which introduce really nifty mechanics for Relationships and for flashback-like effects. My LOST game would have players create characters with no backstory whatsoever, just a description and basic profession ("I'm Jack, a surgeon, and I am wearing a suit and tie"). The rest unfolds with play.
Cheers,
Cam