We put one on my Interstate, and tried to put one on Wizard's standard. It won't work on the standard because it requires separate signal indicators, and the standard has one light to tell you a turn signal is on.
I've not noticed any trouble with my audio system, but then I rarely use it, prefering to run my iPod with headphones since the aux. jack on the radio quit working a few years ago.
It does cancel the turn signal, whether you're ready or not, it's on a timer. Once it cancels the signal, you must still manually cancel it as well or you cannot signal again until you do. I've always left me signal on when I pull into a gas station, because sometimes I'd forget which way I came in, and knowing I turned right to get into the station tells me which way I need to turn to go where I want instead of back the way I came. You'd think I was a blonde or something! Anyway .... it cancels the signal while the bike is off apparently, and I'm still getting used to the fact my turn signals don't want to work when I pull out of the station.
It also flashes the turn signals several times when the brakes are applied, unless the turn signal is on.
And it gives me four way flashers (and wigwags) with a little effort. I've used them quite a bit since I got that feature.
Would I buy another one? Probably not. But I also have a habit of randomly "canceling" my turn signals as I drive down the road. I'll do the cheaper four-ways on the other Valks.