My point is not that the compatibility statement isn't true, its that the statement is potentially misleading for people that get the board and find it doesn't run some popular library from the Arduino playground.
The issue is easily resolved by clarifying the “compatible with the Arduino software” message. Perhaps the site could say that the board works with all of the current Arduino distribution examples ( I presume it does, this would seem a minimum definition of compatible). And I think there should be a note clarifying that sketches and library code that make direct access to resources like timers and ports may need to be modified to function correctly.
It's great to see the Sanguino filling a need in the quest for more powerful hardware to run software developed by the Arduino community. I am sure it will do well. But a little more clarity would help avoid potential disappointments if a needed library won't run on the board.