Great job, there is just one thing that keeps me from using this one over xSnes9x, especially as I am playing Ys IV on it right now: I have a not really small collection of roms for the Super NES on my Xbox and it takes really a looong time to scroll down to Ys IV
So how about adding:
- a favourite browser into Zsnesbox
or
- analog sensitive scrolling with the L/R or the analog sticks (in xSnes9x the scrolling gets really fast if you push R hard)
or
- scrolling through the roms by letter with for example pushing left/right like in Xports emulators
or
- at least an option "Bottom of Dir", I think it would be more useful than the option "Top of Dir"
And no, sorting the roms for example by letters/groups of letters in different folders is no option for me, using xSnes9x who has the first and second feature is easier

Personally I am not so happy with the new "no preview" picture as also with the BGM, as both are not Super NES related (the music is a remix of NES Castlevania music and the picture shows charcters from Paper Mario, what never showed up on the Super NES). Well, maybe just a matter of taste

Edit: The same goes for the Metal Gear sound effects. They are imo not only out of place in a Super NES emulator, it feels also strange if the one moment you hear a sound effect from Super Mario and the next moment one from Metal Gear Solid.