Battery issues aside it provides good performance and nice material feel, whilst not the cheapest product in its class isn't that expensive as audio gear goes.
However I would advise trying before buying as if your device can drive your headphones to the required volume you probably don't need an external DAC/amp. I wish I had a pound for every time I have heard someone complain that they have bought a DAC/amp based on the usual subjective reviews and found it makes no difference.
Also, the form factor of the Mojo seems to be love it or hate it, it strikes me as an awful design for mobile use.