By watching normal non-programmers people like my girlfriends and programmers people like my colleagues with whom I worked closely. Former just don't do any Ctrl-anything during the writing. The later simply never needed Ctrl-S, just like I. Autosave really works in the most common tool, Word. When my girlfriend lost her work, it was never for the autosave, but for manually saving over something she did before or Word corrupting the file during the save (the corrupted file was still luckily readable by OpenOffice).