Well, I can say with absolute certainty that they’ve cast the right hair for the job. If I was going to cast any hair for the role, it would be his. That’s Time Lord hair, right there.
Whether I’d have cast the rest of Matt Smith I’m less certain, but since Moffatt apparently shared my instinctive desire to cast someone older I’ll have to assume his audition was Just That Good. It’ll be a looong time before we find out for sure.