As a Highlander freak I can tell you that yes, the sole movie was bad enough (It hurts...) and the original has little extras, but the special edition has a lot.

Besides the attempt to change the whole "Immortals come from another planet" thing with an alternative less stupid story (at least they tried...) Disc 2 has a many documentaries, deleted scenes, the original promotional reel and the Original Theatrical Trailer.

I own both version and believed or not, the special edition sucks *less* than the original, it still sucks, just in a lower scale.