Since you said desktop environment, my answer will only be in that one aspect. For instance on Windows or OS X, start iTunes or Spotify. Switch away, while it's playing, I can hit the play/pause button and the music will play or pause. All without even bringing the app into focus. That would bolster the shortcut usefulness of multi-tasking.

It doesn't. In fact, I'd have to say that you've missed my point wholly. As far as it goes, Maemo got multi-tasking on a mobile device more right than anybody out there. But to be honest, what people have listed as examples are rather poor examples and not ones I'd consider prime for analogies or proving points. In fact, I'm equally guilty of this myself.

By multi-tasking, people are highlighting a strength that I honestly think just doesn't matter in their usage descriptions. Great, you like to see Stellarium change between night and day. That's less than 1/4th of your screen where it's doing so in that minimized/multi-tasking view. Not something I'd call entirely useful by a long shot. You like to see a screenshot of what song is playing via the multi-task view and you can see the album cover. Guess what? Android actually does that too without a widget in 4.2.x (I think it did it in 3.x, but don't quote me).

Multi-tasking is only as useful as it is to each and every user. Not just specialty cases. And pertaining the controls, trust me. I truly enjoy the expanded controls that BB10 grants me. Listening to music, switch out to the multi-task view, switch to an e-mail. Switch back to multi-task view, I can pause or stop the music from the multi-task view since the controls are now there. That's missing from my N9 and from what I remember, from the N900. It's a movement to functional mobile multi-tasking in my very humble opinion that's beneficial to all users.

But let me iterate one thing. Maemo got it more right than Android. I truly don't mind admitting that. They brought so much to the table that I compare my user experience to Maemo 5 and Harmattan and will not accept much lesser.