"but the X300 marks the most significant change in its design"
did you miss the x41? you know the tablet. yeah, I would think that the whole swivel-touchscreen would be the most significant change. look; after that they have released more tablets following the major change that occurred in the x41. it isn't all that strange for an ultralight either, there have been a lot of tiny thinkpads. yes this one does have a wide screen, but they have had other wide-screen thinkpads too.
if you ask me, yes the some changes are there, but far from the most significant changes the thinkpad line has seen.