If I understood it correctly last time I saw it epsi files are eps files with a comment that contans a bitmap representation of the image. Un*x systems usually have ghostscript and at least some programs that know one of the way to use it (xdvi knowns how to get ghostscript to render into a window, for example). LyX might prefer getting ghostscript to generate png or something similar but either way the bitmap is just a waste of space.
If you are using windows then people probably except you to use word, which can not use ghostscript even if it is installed. You can see a version of the picture if it is epsi, but not it is jsut eps, and not either format on a non-postscript printer. GSview is installed widely but the use of anything not mauled by microsoft, especially if it is GPL or LGPL, is obviously an unamerican activity (at least according to M$'s anti-GPL FUD). LyX can use this fact to show that free software is not only cheaper but also better quality too :-) -- Duncan (-: "software industry, the: unique industry where selling substandard goods is legal and you can charge extra for fixing the problems."
