I have the QB-9, and I can say that it's the best digital source I've had in any of my systems. Over the years I've owned various Benchmark DACs, top-of-the-line Arcam CD and universal players, Oppo BDP-83 SE, Slimdevices Transporter, and a Modwright Transporter (which was very nice).
The clarity of the Ayre is amazing. Soundstaging is excellent as well. Bass is rock solid.
I think the greatest compliment is that it compels me to listen to it. I find myself making time for it. The QB-9 also has me sold on Ayre as a company. Everything is high quality across the board, from build quality to packaging to customer service. Highly recommended.
Oh, and I can also say the I believe the QB-9 is a solid value. Definitely not overpriced for what it delivers.