First of all, I am selling my 2 month old DS for a very good price, PM me if you want to buy it.
Anyways, Directstream sounds musical with optical.
With USB, it varies WILDLY. The USB when fed super clean signal from Windows PC, can be very musical too, more so than optical.
But any power quality issue, any PC issue will show up in the sound. The higher end your system, the more severe the problem will be. Looking at other DACs it is clear that some paid extreme attention to these, eg Bricasti M1, some other even have separate power supply for the digital and analog section and went to great length to isolate the two within the DAC.
So for others in the same boat, a usb card like jcat/sotm will prabably massively improve DirectStream sound quality and get you that musicality at last. And 64bit asio jplay is a must on Windows. I also highly recommend balanced power, although a P3/5/10 will also improve audio quality, note the two are not compatible.
I’ve also had great success with data only USB cable. (Sadly Corning optical USB did not work with DS.)