My Star Wars DVDs have arrived a day early so I'm watching A New Hope right now.  The picture quality is excellent, but the film is not the same as the Special Edition version...  Greedo and Han now shoot at the same time!  After Han shooting first and then Greedo, now they both shoot at the same time.  I suppose when the HD versions are released they won't shoot at all, perhaps the guns will have become walkie talkies...

I haven't noticed any other differences yet.  I'll update if I notice anyother changes.