The Wifi version is also hackable in the same way. You might want to google "Kobo wifi hacks" and start looking around. Unfortunately, it's pretty early in the scene and developers are still working to figure stuff out. I'm not sure there are yet any workable apps written for these devices.

Thank you for then nudge. It appears the platform is rather amenable, and an initial look shows several potential options. Also, the existing firmware can be fully backed up -- there appear to be multiple ways of doing this -- so that borking can be undone, at worst by restoring the original firmware image that resides on an internal MicroSD card.

Unfortunately, my initial editing of an individual ePub title to adjust the font used for <code> was not accepted; I'll be exploring why, as I was trivially modifying some apparently successful instructions for adding custom fonts to e.g. support non-Roman language characters (Cyrillic, Chinese).

I think I'll pick one up after Christmas (via Craigslist) for hacking purposes. I've got a few simple app ideas well suited for e-ink. I think if there's a good community going around this, it might be fun.

It appears one can hack the ePub to change font settings and include an embedded TrueType font (maybe also other formats?), and the Kobo firmware will successfully process this.

I'm waiting for the battery to finish charging to see how Proggy Tiny Slashed-Zero looks. It may be too small, in which case I'll try one of the other Proggy variants, or Dina. (Both Proggy and Dina have TrueType implementations, although I'm uncertain how complete they are. I may have to look around for a better choice of a small-format fixed width font implemented in TrueType format.)