The power button on my Nexus One stopped working. In order to replace the power button, you have to replace one of the two boards. (The IO Board).
I took a friends broken Nexus One and swapped the IO board. Its not as daunting as replacing a screen or digitizer, but give yourself some time. Also the tools provided by ifixit worked perfectly.
There are a ton of little pieces. Label each screw that comes out because only a few are identical. Each go back into different places at *different steps* in the reassembly. Failing to get it right means you have to undo the reassembly and restart.
Also if you replace just the top IO board, you keep all your settings, root filesystem, and IMEI number and bootloader.
It does replace your camera, flash, rear speaker and a few other bits.
And strangely enough the IO board looks like an android.