My perfect reader would support: Epub, PDF, Mobipocket, HTML and RTF
Screen size: A4
But based on a flexible screen ! This way, you can easily travel with it, AND you can easily read any PDF available on the Internet (academic, newspaper etc...).
I don't really need wireless connection or a touch screen, they drain too much power out of the battery.
The right choice would be 2 versions of such a device, one just for reading, the other with a touch screen and wireless connection.
With the right software and content available, wireless connection is pretty neat: download new books while you're sitting in a café, read your daily newspaper/website (the book and RSS part should already work on the iLiad, but not enough newspapers yet, although the e-paper version for Les Echos looks fantastic: http://aldus2006.typepad.fr/mon_webl...les-echos.html
I don't need a touch screen that much but it can be useful for those who need annotations or more advanced software (nothing too interactive for the moment, but an email client could work for example).