>>> Currently the A9 is in PPC G4 territory performance wise.

>> which clock rate in G4 do you think a 1.2 GHz (which I think is the
>> current max) Cortex-A9 roughly resembles performance-wise?

> I believe they're quite similar clock for clock.

Also here, found some NBench figures of both to compare.

Cortex-A9: http://www.powerdeveloper.org/forums/viewtopic.php?p=14836#14836
G4: http://amigadev.free.fr/powerpc/nbench.html

Result scores (for 1.0 GHz each):

Cortex-A9 (one core of dual-core OMAP4):
- MEMORY: 6.52
- INTEGER: 6.19
- FLOATING-POINT: 6.82
- BYTEMARK INTEGER: 25.4
- BYTEMARK FLOATING-POINT: 12.3

G4 (scaled from 400 MHz | scaled from 1.4 GHz | scaled from 1.5 GHz*):
- MEMORY: 7.49 | 5.76 | 4.49
- INTEGER: 6.69 | 8.27 | 5.76
- FLOATING-POINT: 9.24 | 6.47 | 9.02
- BYTEMARK INTEGER: 20.7 *
- BYTEMARK FLOATING-POINT: 16.3 *


* my machine