Recent review from Srajan over at 6Moons:
http://www.6moons.com/audioreviews2/denafrips/2.html
On discrete R2R: "R2R DACs aren't novel technology but the very first D/A conversion approach. Strictly speaking, using discrete R2R is no technological innovation but regression. It's the D/A integrated chip which is the embodiment of technological progress. From an audio perspective, it's simply not true that technical advances must automatically produce better sound. Sound is a simple yet complex matter. Sound is simple because it uses the most basic electronic knowledge. It is complicated because it also involves endless knowledge from outside the field of electronics where electronics suddenly become the most basic requirement. A good designer must also understand music cultivation, the recording processing, replay in a room dealing with specific acoustics and more. Good sound is about all of these intangibles. To reproduce high-quality music is not an easy task. To design good equipment, you must first know whether the sound is right or wrong; and then why it so. Playback must get as close to the recording as possible. So the designer must be able to recognize sonic differences and their poor aspects and possess the technical know-how to overcome them by electronic means.
http://www.6moons.com/audioreviews2/denafrips/2.html
On discrete R2R: "R2R DACs aren't novel technology but the very first D/A conversion approach. Strictly speaking, using discrete R2R is no technological innovation but regression. It's the D/A integrated chip which is the embodiment of technological progress. From an audio perspective, it's simply not true that technical advances must automatically produce better sound. Sound is a simple yet complex matter. Sound is simple because it uses the most basic electronic knowledge. It is complicated because it also involves endless knowledge from outside the field of electronics where electronics suddenly become the most basic requirement. A good designer must also understand music cultivation, the recording processing, replay in a room dealing with specific acoustics and more. Good sound is about all of these intangibles. To reproduce high-quality music is not an easy task. To design good equipment, you must first know whether the sound is right or wrong; and then why it so. Playback must get as close to the recording as possible. So the designer must be able to recognize sonic differences and their poor aspects and possess the technical know-how to overcome them by electronic means.