Pros: Sturdy, appreciable improvement in sq
Cons: Looks a bit utilitarian but that is all
I bought this to give my iPod (320Kps files) a boost and immediately noticed a difference. The sound became more relaxed and allowed more detail to percolate through. It seemed to take the rough edges off without making the sound mushy.
Since disposing of the iPod and moving to a Cowon X7 (FLAC files) I still hear improvements but maybe not as night-and-day as before. I use a variety of headphones and IEMs but I have not noticed anything significant between them using the Voyager, they all seem to benefit from having the amp in the signal path.
The amp itself is solidly constructed and feels like it could survive the tribulations of using it on the move. However it does add bulk, approximately the same as an iPod, and I found it awkward to use this when commuting on the train (when arguably the benefits are reduced still further due to ambient noise) but this would be true of any headphone amplifier. However used now in the office where mobility is less of an issue I enjoy all of the benefits with none of the downsides. It does not look glamorous, there are no shiny chrome bits or brushed aluminium but this neo-industrial look is not without charm.
I used this amp every day with my Cowon (but not with the RoCoo P as this does not seem to need any help) until recently and then sold it to help fund another (more expensive) headphone amplifier. Recommended.