>...especially with ARM11. Cortex-A9 offers about twice the performance per clock and core compared to ARM11, thus quadruple the single-core performance when clocked at around 1.5 GHz.

Yes, and faster versions on the horizon.
While I am impressed with ARM in general (and like the EfikaMX's design), the Cortex-A9 is the most impressive variant so far.
If it wasn't a little buggy, I would already be using a Pandaboard.
And TI next revision look even more promising.

If we're going to replace our PPCs, I'd prefer it be with a MORE powerful solution (not a less powerful one).