Not yet hacked, but I've found that ramping the sound quality up to 7 and enabling all of the various checkmarks but "play it loud" on the sound screen gets rid of a large amount of the distortion.
My biggest problems other than that involve using the Sixaxis as a controller. For some reason the damn thing is working completely fine other than the square button which is recognized when I configure the stupid controller but doesn't work when I'm actually playing or getting the damn thing to run in full screen mode. I'm sure the second one can be fixed easily enough.
I think the thing that pisses me off most about the SNES9x sound problem is that the devs that I've seen on the snes9x boards are not fond at all of the PS3 and have no intentions of trying to help us out - in fact all they said was to complain to sony - yeah right that'll work.
I know that simple software modification can fix the sound problem so hopefully someone picks up on a PS3 version of SNES9x. I mean it shouldn't take long at all...all we need is a sound fix.
I checked the official yellow dog page and apparently one of the mods is working on getting the gnome version of an SNES9x frontend up and running on YDL sometime in the near future. I'm excited to see where that's gonna go.