I got my DVD today and it seems that in the dub on the new DVD, a lot of Phil Hartman's ad-libbing has also been removed.
He only speaks in the scenes where Jiji originally spoke in the Japanese version. No redubbing has been done (since that would be impossible), but Jiji just speaks only when you see his mouth move.
Also, all of the music used in the Japanese version is now present in the dub. Disney changed some music for older releases of the dub, but now undid those changes.
It seems that when Disney "digital remastered" the dub for this newer DVD, they must have still had the voice-only tracks they used to create the dub back in 1998. They must have overlaid them over a clean Music & Effects track from Japan and probably used the Japanese version as a guide.
As for the video quality, it is very much improved over the DVD from 2003. The credit sequences on the English angle are no longer blurry and fuzzy.
And in response to Leaping Larry Jojo, it seems I can toggle on the fly between audio tracks on the new DVD. But in order to change angles, one would still need to go back to the main menu. I don't know why Disney allowed this for the DVD of Kiki but not Ponyo.