I finally vanquished my distaste of upstart, and ported USBNetwork (the K2/3/4 one) to the K5 (Touch/PaperWhite)!
(It's available in the
first post, of course

).
That means a working SSH + usbnet on boot, OpenSSH, auth via pubkeys, no sshd daemon hanging around when you're not in usbnet mode, scp & sftp, wifi, and the usual set of USBNetwork tools.
You don't need to uninstall simple_usbnet, the installer will take care of everything.
(As usual, it defaults to dropbear, but I recommend switching to OpenSSH once you have a working config, because it's way faster [no update on the libtommath regression front, so dropbear is still taking forever to auth]).
Did I mention I hate upstart with a fiery passion? Because I do. It took a few read-through of the upstart cookbook to wrap my head around it, and settle on the 'best' way to handle it, without resorting to 7 billions upstart jobs & signals... Thankfully, I got it mostly right on my first 'live' test. I'll stop ranting now, but I'd be curious to know if anyone actually *enjoys* writing upstart jobs, because, personally, it just took 1st place over qmail in the 'worst thing to configure, ever' tournament...
I updated the Wiki, too, that made the whole 'USB networking' block a good deal simpler/shorter.
Since this is based on the K2/3/4
USBNet package, I'm not mirroring the patchset (found in the kindle-x-compile-tc.tar.gz tarball) here, but it's available in said thread, and applicable to both version of the hack

.