The main difference I see is that you set both policy.max (in cpu-omap.c) and policy->user_policy.max (in cpufreq.c) to 600000, while I do not change files outside arch/arm.

I admit I'm a little lost, rereading this thread. What different behaviour do we try to explain?

You also use highest voltage level for all frequencies 600 and above.
I reduced the voltage levels of all frequencies 550-600, and only use the second highest for above 600.