Which is funny, because it's the only app that I've found even remotely (pun intended) useful. I guess because Remote Desktop is the only thing I use in my typical computer usage that I don't mind running full screen.
You're basically saying that any application that has state that takes more than a second to save/restore is better off not being a metro app. Which is incredibly limiting.
Strangely, quite a lot of the metro apps I've tried do this horribly. Pinball (another MS app), for example, basically just closes when you switch away from it. If you switch back, you go through the loading and logo screens again (takes a while), then it will ask you if you want to resume your game. It's a horrible experience.
The end goal may be laudable, but this simply isn't working well enough yet. I end up closing every metro app anyway because I don't want them to clutter my alt-tab, and when I don't want them to close, they get suspended leading to excessive resume delays.