Rosetta worked pretty well.
The alternative is a full port of Win32, which I imagine Microsoft considered and rejected. Even after they incurred all the time and development cost, ISVs would still have to at least recompile.
Not much commercial software but the regular open-source windows stack works.
Link please?
I'm talking about the management decision that only Metro apps can run on RT, which is such a stupid limitation that even Microsoft sees the need to bypass it to get Office on an RT tablet.