I actually really didn't like Tron's dub voice. It sounds too chilidish and high-pitched. The Japanese voice can pull of being childish and being serious at the same time and I don't think that this English voice is nearly as good. IV's dub voice was fairly decent, but I agree that it doesn't fit with him. It sounds too calm and honestly far too old for a teenager. Maybe it will sound better once IV gets to show off how crazy he is later on, but it doesn't fit him. I wonder how they'll handle his fanservice catchphrase.
Droite and Gauche probably have the best of the new dub voices. Their voices actually fit pretty well. Although I thought that Gauche sounded a bit too gruff and loud at times and being voiced by Jason Griffith made me think of how small their pool of voice actors is, but it still worked better for the character than IV and Tron's dub voices sounded to me.