Pardon my ignorance, but while reading the many overclocking threads, including this outstanding summary, it seems to me that there is a huge variation in the types of overclocking that individual units support.

Might I ask why this is the case? And is there any remedy if, say, the ideal or ulv clocking profile renders one's n900 unstable? Any further kernel tweaks that can make it work?

For instance, it seems to me that some people simply type "kernel-config load ideal" and live happily ever after, while others struggle to make ulv work with 800 Mhz. What differences (e.g., build quality, quirks in hardware, etc.) make the latter "unlucky".