>I'd say the inclusion of the SPEs is what makes a Cell a Cell.

THAT'S an interesting definition Andreas.
From my examination of the two Cell processor that were made and the immediate potential successors, I thought the shift to a Power 6 successor (as the core CPU) was really significant.
Of course, the SPEs have also evolved. CellBE's SPE were much less powerful then its sucessor's SPEs.
So both the Core CPU (PPE) and its attendant SPEs continue to evolve.
Power7's core processor should be far beyond any previous PPE core. As we don't yet know how much improvement has been made in the SPE's perhaps my biased focus is unjustified.
Is it a Cell derivative? Yes, I guess it is. But as a Power6 successor Its also so much more.