Even such a simple thing as blacklisting faulty module need rebooting (although I admit that it doesn't need powering off/on and AFAIK nothing require that). modprobe -r used on certain modules (bq27x00) can cause watchdog to reboot device anyway in few minutes, in less desireable moment - just as side note.

Personally, i wanted to turn device off via bootmenu few times, when I realized that my battery is too low to do safe backup or restore. Then, I change battery to fresh one - that obviously require powering off, at least until I finish my hotswap-easy-now ( ) mod.

Also, many times I do backups before going to sleep, after testing some new things. Then, I need to restart N900, wait for initial boot completion, type full-lenght lock code, type (or cancel) PIN, wait for boot to finish, just to turn device off as I do for night. PITA.