Assuming you were planning on getting a Surface Pro to do real work on (typically requiring a desk, keyboard, etc.) can't you connect an external hard drive to it? External storage space is extremely cheap. If you're making the argument that it should come with everything it needs to "just work" out of the box and be ready to go, I can respect that, but I don't see how you could call that a laptop/desktop replacement. When I personally think of laptop/desktop replacement I think of at least something resembling a docking station: external monitor, keyboard, mouse, et al. Part of that would have to include an external hard drive for me.
I do agree that a rich docking station experience is extremely valuable and one Microsoft should pursue to help show how well Surface can fit into an office environment. That said I don't need an external hard drive for my laptop today (dock or no dock). Having to lug around an external drive for travel really defeats the portability factor.
IMO, Microsoft had an opportunity to do better than the competition here and once again they chose the "also-ran" strategy. They really should have stayed away from the 64GB version and just issued a 128 & 256GB versions. If they want to play smoke & mirrors why not market it as "64GB SDD with a 64GB FREE UPGRADE". I think people would forgive the fact that the 128GB version only has 83GB available space if they think they are getting an extra 64GB free in the first place.