[Cdesja5]

The Mini's firmware is the same as the Kobo Touch or the Glo's referred to by ciscopixie, and so the Mini's differentiating factors are that is is smaller and does not have the lit screen, not the firmware which works the same across the 3 devices.
I don't find it too small to read and suggest you try one out to see if that is an issue for you. For me it's size is it's main selling point and makes it very light and easy to carry in a pocket or purse. I find that I prefer my Mini to my Sony T1.
You can add your own fonts to Kobo ereaders and that is a big plus for many users.
Calibre works well also; Kobo Touch driver (used by mini and glo) allows for adding your own custom shelves for your device using Calibre.
Check out the Kobo threads, generally any info about what can be done on one model (ie. Touch or Glo) can be done on the others.
You generally see posts about Kindle, Nook etc. in this thread because they are the 2 best selling brands in the US; Kobo is Canada's #1 brand with about 50% of the market there.
Epub3 support is firmware related so a future upgrade could take care of that wish...but not the light unfortunately!