Just tried out your plugin, and I think it is terrific! Really nicely executed.
The only issue I found was that files uploaded via the fieldtype file are not registered in the media library, nor are they attached to the post. Custom Field Template was able to do this, and I am thinking of merging the code together here sometime soon.
Hi lag47, thanks for the great feedback. This plugin is designed to specifically _not_ interfere with the media library as we wanted to allow that to be used separately with the native wordpress interface.
It is true however that the plugin does not remove files from the server if they are removed from a post/page. It should probably do this so as not to litter the server with unneeded files. Will include this in the next update.