I bought the new "Goodfellas" DVD set. The differences in the film are subtle but worthwhile. The video quality is improved a bit. The sound, which was pretty flat considering the nominal 5.1 format and all the terrific music, has been improved. There's more definition and the music sounds somewhat better. The voiceovers have been re-recorded and now have a hollower sound, or so it seems to me.
The second disc has extras. There's a longish feature with interviews by cast members and crew that are mostly paens to Martin Scorsese. He deserves the praise he gets here, but there aren't many insightful comments or much new info, so this mostly comes across as a commercial for him. You will hear Paul Sorvino's real voice, which is beautifully modulated, and with perfect diction. (BTW: He often narrates programs on A&E and the History Channel, and is an opera singer.) There's also another featurette showing Scorsese's notes and drawings, and how they were realized in the film. I found this one really boring. The main disc, with the movie, has background commentaries by various people, which I will get to when I have a chance.

Overall: What I've seen so far doesn't justify my having bought another "Goodfellas" DVD set. By comparison with two later-release DVDs that I own, "Apocalypse Now Redux" was worth it because it's a different movie--and the audio is tremendously enhanced over the original. The "Godfather Trilogy" boxed set's audio and video weren't significantly better than the 25th anniversary VHS set, IMO, but the extras disc was worth the price by itself.