[arp242]

I've been hired and the quality of my cover letter was specifically cited as a reason (also later confirmed by the HR lady who tried to hit me up when she was really drunk, when she kept banging on about it for some reason, but that's a different story).

So some are reading them at least, n=1 etc. I usually use them to supplement my CV, by pointing out things that are relevant for this specific position, or listing things that aren't on the CV (and usually shouldn't be on the CV) but still relevant, like a specific open source project I contributed to, or something from my personal life that relates.