"evince" from gnome (linux) reads comics too.

My ideal reading environment is a big couch, a book open (a real one) and the NDS with kanji sonomama set up, just in case.

Leeyes is pretty good for reading manga on Windows:

http://www3.tokai.or.jp/boxes/leeyes/

I'd recommend getting Susie plugins for zip, rar, and JPEGs. Makes it a lot nicer to use.