When viewing posts with large images (or in fact anything that forces the post to be rendered wider than the viewing area in google reader), the iframe's scrollbars are way down at the bottom, and you have to scroll down to the bottom of the post to get to the horizontal scrollbar, before you can scroll across, and back up to the top, to view the other piece of the post.
As an example, view the Diesel Sweeties RSS feed:
http://www.dieselsweeties.com/ds-unif...
Scroll down to the post for April 6, 2008 - it is very difficult to view the entire comic without scrolling up and down and left and right.
I appreciate that putting posts in an iframe means you're a lot safer from cross-site scripting attacks and so on, and that this constrains what you can do with the post, but is there not some way to make large images draggable, or scrollable with the keyboard?