I normally read Japanese manga and the text is pretty clear on my PP, albeit a tad too tiny for my liking. I've seen
this video on YouTube and it looks pretty acceptable to me, so I'll probably try my luck at a Sony reader since anything bigger would be too expensive.
Edit: Here's another one that I found on YouTube. The 505 seems to be able to handle comics well too.
http://www.youtube.com/watch?v=tePc-KxHqak