There's no a easy way to boot in various OS's. Multiboot needs special kernel that recognise it and show the menu.

There is a kernel for Maemo and for NITDroid. But the kernel that MeeGo is using not work. You can boot to MeeGo with Multiboot, but can't back to other OS (Multiboot is no more showed).

I have MeeGo and NITDroid in my memory card, but after booting in MeeGo, I need to use Flasher to come back to Maemo or NITDroid.

Maybe there is a way to MeeGo itself reflashes the device....but it's beyond my knowledge.