Unless MS release some actual sales figures, there is no way to know if 'sold-out' equates to hit or lack of stock.
Even if they did release numbers, what would you define as a "hit"?
1 million units? 500K units? 100K units? 50K units?
I think it's safe to say that no single electronic device with a price tag of $900 or higher has ever sold 1 million+ units over a single week, including anything that comes with a fruit logo on it.
It would be far-fetched to think the Surface Pro has achieved anything remotely close to 1 million units in sales. I would consider even 50K units sold over the past week huge considering the price tag.