I know true multitasking is great but can someone provide a real life example where it is useful on the phone?

I'm at a point where it feels like it is time to retire my N900, so doing a lot of thinking about what should be next. Been salivating about the N9 for a long time but certain apps I need are not available for it. Really liked how 8x feels in hand but WP is a no go for the same reason. I have philosophical disagreements with Apple so it has to be Android. HTC One X seems like a phone I can live with and in the US ATT has refurb ones basically for free on a 2-year contract.