The paula hack for AHI audio works pretty well, so I expect that it won't be a big issue. The question I would have is how many people are buying the AmigaOne for it's backward compatibility. I'd imagine running UAE on it would give enough speed and backward compatibility for anyone.
Even if the backward compatibility isn't great, wouldn't you be buying this to be on the new frontier anyway.. I guess I maybe am silly but I wouldn't buy an A1 to run old software, I'd be content to have one to run the new software that comes out in a familiar enviroment. Long ago I used to have people ask me if the Amiga was "IBM compatible" and I had to answer the question "yes" with an add-on, but it's so much more than that so why would you care..
-Don