Its a Chinese detector that works ok, but they have had build quality issues in the past. Given the choice, I would go with a more established detector company that stands behind its products, such as White's, Garrett, Tesoro, Fisher, Minelab, Bounty Hunter (midrange or above models only), or Teknetics. (I am sure I missed a few good brands).
I have never used an MPX detector, but I see them on ebay and at kellyco. Depending on where it was bought from, there may be service options.
The question as to if its worth using is hard to answer - what are you looking for? I prospect for gold with my metal detectors - there are only a few that are really good for that purpose, and the MPX is not one of them. If you are mostly interested in Coin Shooting or Relic hunting, or want to work salt water beaches - these would determine what your better choices are. All detectors are compromises to allow for different hunting conditions - there is no one 'best' metal detector.