Windows Phone 7 doesn't multitask. It doesn't copy/paste either. It's like iOS three years ago.
The absence of copy/paste is supposed to be fixed after the initial release. Not sure about multitasking. From the early reviews I've seen, it's not "like" any other smartphone.
I believe it's an issue of CPU and power consumption control. Might be nice to have full multitasking but I haven't run into any application on my son's iPhone that I want running in the background that isn't one of those WP7 native applications. Of course I don't use a smartphone continuously through the day - it's possible I just haven't found that uber-app I want running at all times.