http://www.youtube.com/watch?v=RtrKo5UWpco
Here is a video of the Kindle vs. Sony, if you are very concerned. With non DRM books, you can change the font, I believe, but not directly on the reader, rather in the file before you load it to your Sony reader.
Here is the written review of the video I've linked.
http://blog.the-ebook-reader.com/201...-video-review/