Those extra features are nice - though a emu would need a header info box for them to make any difference to someone using the rom, inaddition unif would be a huge difference over .nes format in my oppinion because of the fact that it reduces excessive mapper numbers cause by more than ines mapper, mapping to real mapper (should also stop wrongly labled mapper roms)(unless its a lazy ines traslation i.e not checked in first place).
Also it should be relatively easy for demo rom authors to translate their own roms as they just sandwich their prg rom + chr rom in a unif header - unless I misunderstand the unif spec.