I've actually used "Who's hiring" in the past. Two things made it very useful to me:
1.) It tells me something about the company. At the very least, it tells me that at least one founder/employee/etc. is reading HN.
2.) I can leisurely check out what the company does without making any sort of commitment (even just a phone call/screen).
Both of those advantages go out the window when recruiters are involved.
And BTW, I have nothing against recruiters. I just wish there was one jobs related page on the internet that didn't have them.