I don't see the /point/ of running multiple OSes on a desktop, and especially not on a phone.
I mean, why do it? The only reason I can think of is "applications from one OS not working on another".
I think the /solution/ is to simply have /one/ good OS that can have anything you want loaded on it. Maemo's a good example: We don't /need/ to dual-boot Linux usually, because we either have it natively or can run a Debian(etc) chroot.
It's the same with Android: Instead of focusing on making Android boot, we should be thinking in terms of Alien Dalvek and making our main OS(Maemo) better. That way, you get the same advantages of having multiple OSes, without the time spent switching, the loss of processing power/worse battery life...

Now, perhaps Maemo's not going to be the end-all-be-all OS, but we should be thinking in terms of that instead of VMing everything(which /will/ reduce performance).