Well, I've somewhat successfully upgraded my 64GB Microsoft Surface Pro with a 240GB Intel 525 mSATA SSD. I can confirm that what's in there is an industry standard mSATA Micron C400 SSD, and that most likely, any mSATA SSD will work just fine.
I do have a warning however - I don't see any way possible to disassemble the Surface without destroying the touchscreen functionality. The reason for this is because the touchscreen connectors are slim ribbon cables that are glued on two sides. The side with the actual connector is glued to the back of the display and has a weak adhesive. The connector contacts are made of a conductive powder, similar to a temporary trace made by a circuit pen. The back side of the touchscreen connector is glued onto the Surface case with the super sticky 'tar' like adhesive described in the ifixit teardown.
The combination of the weak adhesive / powder contacts on the connector side and the strong adhesive on the back means that opening the Surface destroys the touchscreen connector by pulling it apart:
A simple repair attempt using a conductive pen looked promising but was unsuccessful:
If you take a closer look at the ifixit teardown (step 6), you'll notice that one of their touchscreen connectors has been cut out (lower left) and the other is missing (lower right):
Their tablet was never meant to function again by appearances...
The one positive note is that the stylus still works normally, so even though finger touches don't register the touchscreen is still usable via stylus.
Here's one last picture showing 190GB free on my C: drive
Definitely not a clear win though since the touchscreen is crippled. Any other thoughts out there on ways to revive the touch?