Personally I wouldn't mind having Symbian^3 as an alternative. It adds to the wow factor of course. I am currently dual-booting android and maemo. I use Maemo all the time. It is superior to Android in nearly all ways (in my opinion). At this point I only boot Android for games, and go back to Maemo for anything else.

In my opinion Maemo is superior to iOS, Android, Symbian, Windows Mobile, BB OS and Palm OS. But would I like to triple-quadruple-whatever boot all of them? Would I like the possibility to use different OSes and interfaces without having to pay anything? Yes I would. I don't think I dont't think I would ever consider switching completely from Maemo. But it wouldn't hurt to have the liberty of using other OSes. I say port anything you can. It only adds to possibilites, not reduces existing ones.