I just built the latest 2.6.28.10 from extras with a 500mhz max DSP and these timings for the MPU:

125 / 250 / 500 / 750 / 900

Rock solid, and SO FAST.

Finally I can use the mafw equalizer without stuttering. Web pages render much more quickly. I ran it at full load for 15 minutes (bzip2 + equalized media playback) and the keyboard surface stabilized at 32C.

What an amazing machine.