So here’s the story on multitasking in Windows Phone 7. According to the director of Windows Phone:
The core operating system is a modern multitasking operating system. If you play music for example, the music will play back as you navigate around the experience…if you’re using email, we have great support for push email and that happens in the background.
For third party applicationswe’ll get into a lot more detail on this in MIXbut we have a few ways we’re going to make sure that third parties can bring their value to the user even when the app is not running. Live tiles are an example. Data feeds in the hubs are another example for some apps.
It looks like multitasking will work much like it does on the iPhone, but with a little more flexibility. Certain apps will be able to run in the background (meaning, default apps like mail/music/etc) while third party apps will be able to tap into its own tile on the front page (and thus become a data feed) or perhaps make use of a system-wide notification system (like on the iPhone). Unless there’s a big surprise in store from Microsoft, switching applications will be much like on the iPhone. You’ll go back to the home screen, open the program launcher by swiping right, and open up the app you want to use. Hopefully if this indeed the reality of the situation, you’ll be able to assign a hardware button to quickly launch the program picker (shown above).