The box does not appear at all in Firefox 6 (haven't tested in other versions)
Changing the Offset percentage doesn't seem to matter in Chrome 14 or IE9. The box only appears when the specified HTML element comes into view that the box shows (I guess = 100%).
Unchecking 'Excerpts' does not work. Setting # of words to 0 is a work-around.
It would also be nice to have an option for a custom YARPP template different from the YARPP template I use after my posts or at the very least, one that honors the 'Number of posts to show' option.
Generally, I like the plugin, however.