Dear Corwin:
For sure your unit works smooth and fine at 600mhz, but you know, as we can see, there're a lot of hardware implementations when building n900.
My n900 is a crap running at 600mhz, but sexy as hell when 950 overclocked. Perhaps cheaper components here?
So you are right when you don't overclock it, and I'm right overclocking, having in mind that I assume a very short lifetime for my Lehtokia n950 (but a happy lifetime).
Regards.

EDIT: Obviously, it seems Android is a more capable platform, software-related and hardware-related, they are not so afraid about overclocking as Nokia is. When my lovely OC fries, I know what to buy. It's a shame, surely N9 lauch will be delayed... hardware upgrades in development? "When N9 will be launch?... When portrait mode for N9?..."(only joking...)