Most people will have Quicktime, it seems to find its way onto most machines sooner or later; but the question does come up from time to time, people ask "why can't I see GIFs or PICTs?" (I know, I asked it myself once). Given the huge decrease in file size, you may consider it worth a bit of effort expended on customer service to use the GIF. There are bound to be users who find it doesn't work; your readme could suggest installing Quicktime, or for those who don't want to do this, explain how to convert the GIF into some other format. I can't help wondering why the big difference. 10.5 MB -> 1.5MB is a huge leap, and I've never seen a GIF produce such a dramatic saving in file size. Just curious.