Afaik they are working on a new FW to resolve the audio issue and probably some other.
I bought one beginning of the month, 2 weeks later I hooked it up to my white (more yellow) PC Engine, audio routed through my Amp, video to the PVM.
I have to say, it looks quite good - I don't see really a difference with my modded IFU output.
As regards of the audio 'hiss', to be honest, I haven't heard it with any of the CD-based games I tried; even turned up the volume.
So, I can say I am quite happy