Still doesn't matter. Unless you create an ecosystem around your software, I think it still isn't relevant in the larger scheme of things. For eg., can Maemo, Android, WebOS etc all share applications, APIs, drivers, and other infrastructure seamlessly?
The point is you need to end up creating an ecosystem around your offering, which is non-trivial. Even if you do, you may still end up as a niche player. Litl is nice; but how well do you think they'll do against traditional netbooks?
Depending on how you architect your OS, it doesn't have to be impossible.
I have a little Exokernel project I devote my Saturdays to, and we'll actually be able to offer a POSIX-compliant libOS, and run anything that Linux does.
Or, there's always the hypervisor route, on desktops anyway.
The point is you need to end up creating an ecosystem around your offering, which is non-trivial. Even if you do, you may still end up as a niche player. Litl is nice; but how well do you think they'll do against traditional netbooks?