Pros: Size, SQ, Construction, Bass Boost, Battery Life
Cons: None unless you're picky
Like the title says, this CMoy from JDS is killer! Great sound in a small package for less than half of what many comparable amps cost. It adds a nice warmth and depth to the XBA 3s and GR07s I've tried. The 9V easily powers most headphones, even those that are harder to drive. The bass boost is rarely needed, but if you want some extra bump, the CMoy has plenty to go around.
Like many portable amps I was wary about the battery life, especially for something so inexpensive. No worries anymore. I has been playing since mid-morning and it is now 6:45. Also, the rechargeable battery will allow it to play while its charging - a serious step up over Fiio's amps.
The volume knob is very sensitive and the amp will turn off automatically if the headphone cable is disconnected. Great feature!
The only things I can imagine would bug some people (who shouldn't have ANY problems in this price range...) is that the Altoids tin is a little funny (although unmarked tins can be purchased). The lack of gain or impedance control has been mentioned but honestly for everything else you get, that's like missing the sprinkles, on the icing, on the cake.
Thank you Jon for a great product!