Yes, the id3 files are portable. They will be automatically applied to files that match the same name, from what I remember - so you can send them to whoever you want.
I'm not sure you're going to save me "hours upon hours" of work, since I'll have to rename all my files to match your names... Why not just do IMDB searches on my own? Also, any DVD I put in is automatically identified, so I generally don't even need to do the search manually...
There are tools to view and edit id3 tags - these files are not a LinuxMCE-specific format. I believe this is the correct Ubuntu package (though for the wrong version): http://packages.ubuntu.com/lucid/id3
I'm not sure why you would want to edit the tags "in windows"... You know Linux has graphical environments too, right? I haven't ever heard of a windows program that reads ID3 files next to video files to import metadata.