This is a very interesting thread!
If one was looking for PIM functions, and handwriting recognition, a piece of software that would be very interesting to port would be Paul Guyot's OpenEinstein, an emulator for Apple Newton that allows licensed users of the Newton ROM (i.e. those that bought one).
Newton was one of the first ebook readers (1993), though display technology of the time was nothing like as good as it is now.
This is an emulator at present, and requires a dump of the Newton ROM to run. These can be acquired legally by buying a device for a few dollars on eBay or similar. It runs at acceptable to good speed on a PC like my 1.6Ghz Pentium laptop, but as yet slowly on PDAs (so far- Sharp Zaurus, Nokia 770/800/810). Work was being done last year to remove speed bottlenecks by rewriting some functions in C or C++.
Since the UI uses animation, these would have to be removed to make it suitable for an e-ink display, I guess. Is anyone interested in making a port of Einstein to Iliad? There are still thousands of Newton users out there who are looking for a new hardware platform for their favourite device...
OpenEinstein is at
http://code.google.com/p/einstein/ if anyone wants to take a look.
Emulti