For tablets and portable devices, legacy app compatibility will be less an less of an issue as the store gets better options. I see legacy app compatibility as a temporary crutch to make up where new apps haven't been developed. Its not the future of the platform. If there continues to be a significant price discount for RT and a battery life bonus - I think it still makes sense. Remember, Atom is not the only chip platform coming out with a faster new model - the next gen ARMs are on the way too.
Precisely, which is why - from my non-technical perspective - the Surface RT seems to be the more revolutionary of the two machines released by MS.