But you still have inefficiencies in the translation - so the translated app will generally run slower.
Not to mention that there will be incompatibilities and some apps won't run (even Anand's report confirms this). As just one example, if the app is based on Flash, it's going to have trouble - since the latest versions of Flash won't run on Dalvik. And since we heard endlessly how critical Flash was, that's an important deficiency.
Depends on the translation. ARM is simpler than X86 so for the trickiest part is making sure the bindings to the OpenGL libraries transfer efficiently.
Intel makes very very good X86 compilers. They have the engineering chops to do this reasonably well. Obviously recompilation is preferred and for Samsung the large players can be convinced to do so.
Flash is, and always has been, a non issue.