I've tried a number of methods to get video to play in Firefox or IE mostly using javascript (kaltura) players. I was able to get the different versions .mp4 and .ogv to play however when applied to WordPress, not so simple. This is by far the easiest solution to apply to WordPress. Please continue to develop this plugin. It really enables the power of blogging with video ownership.
http://wordpress.org/extend/plugins/videojs-html5-video-player-for-wordpress/
