In the hopes that someone else might benefit from this info ...
I purchased a Tor ebook from Kobo because I knew it would be DRM free. So when I went to my Kobo library, lo and behold, there was the shiny blue "DOWNLOAD EPUB" button. Yay!
But when I click said button, I get a "whoops! 404" error. Over and over and over ...
... for hours.
Crap! Oh well, I can always go the obok route (yuck, but doable). Except after I sync my Kobo Desktop (and my shiny new book appears in my Kobo Desktop library--Yay!), my drm-free book doesn't show up in the obok list of titles. Double crap.
So I go spelunking in the AppData/Local hell where Kobo Desktop hides its very ridiculously-named and fairly-unidentifiable kepub files on Windows, look for the most recent one, copy it out of there, slap an '.epub' extension on it and pop the hood to discover a drm-free kepub version of my ebook. The ebook I decided to buy because I thought it would be the easiest to download and put on the reader of my choice (which is one of the main reasons Tor Books gives for going DRM-Free).
Cleaned out all the kepub gunk (changing it from an ePub3 to an ePub2 just for good measure) and put it on my tablet to read!
Yay?
So yeah ... note to self: Buying a DRMed Kindlebook and turning it into an epub is quicker and easier than buying a DRM-free epub from Kobo and turning it into an epub. Go figure.