My first impressions of the rDAC were not so good, compared to my Musical Fidelity M1 DAC it seemed bright, fatiguing and lacked detail.
Quality was particularly bad using Voyage MPD from an Asus eee netbook (but mostly the fault of the netbook).
I tried a minor wallwart upgrade from Maplins (no appreciable difference) and later got a Teddy rDAC PS.
The TeddyPardo powersupply totally transformed its performance. Bass was more clearly defined and precise, sound staging improved.
This (or an equivulant power supply) upgrade would noticeably increase the cost but even at the 500GBP mark, I am still happy with the price/performance ratio.
As I type, I am listening to the rDAC with a Musical Fidelity M1 CDT transport as source (connected via coax) and the sound (to my ears) is as good if not better than listening to the same files via USB.