The former, "zeroclock is the preferred means". And that's what maemo is all about. Obviously "normal desktop" distros (and apps) don't worry at all about power consumption. Maemo does, see testing and development guidelines. And the allegedly poor battery life of N900 is merely from installing apps that are poorly tested and not obeying the basic rules. There been a few, particularly desktop applets. Usually installed from maemo-extras-devel, completely ignoring the warnings.