Wow, right from your article, "so it’s not a true multitasking OS" including "The disadvantage obviously is that developers who actually have a legitimate multitasking need (like music streaming) just can’t do it right now."
Face it, WP7 does now allow third-party multitasking like Android, something I believe you considered to be a fatal flaw for the iPhone.
Along with the notification service, Tombstoning comes very close to a true multitasking experience for the end user for most types of applications without the disadvantages of true multitasking. Combined with the hardware back-button, the user will experience a kind of flow in daily use without always having to go back to the start screen. This lets the user multitask much more intuitively than for example on the Apple iOS even thou the phone actually pull off a David Copperfield.
The end user is God in Windows Phone 7 – like it or not, developers and nerds! (no offence, that’s me too)
The advantage of only allowing the Tombstoning model is that lazy developers (and trust me, developers are lazy) can’t just let their applications continue to run and drain battery in the background while clogging up the phones memory until the phone becomes unusable.
As long as we’re clear that the multitasking of WP7 is as good as on the iPhone. Android has a bit better multitasking system, and none of them are real multitasking like old WinMo.
If you want to say WP7 doesn’t multitask, then you have to say the exact same thing about iOS. They’re the same multitasking approach.