How well or poorly designed is the airplane J-31?

Compare to european, US, other Chinese airplanes, asian planes, how well or poorly is J-31 designed?
What are the aspects that makes it a good plane or suitable for certain task. Or what are the flaws in its design making it unable to or poorly perform certain tasks.
What are some of
modern (post WWII) well designed airplanes (commercial and military) in your mind.
How is J-31 compared to Japan, Korean, taiwan planes?

answer:
This question has a couple of features, I will address them one by one.

The J-31

It is very difficult to tell whether this is a well designed plane because we aren’t quite sure what it is designed to do. It certainly looks like it will fly, so at least they got that right (unlike Iran’s new fighter) 

From what you can tell from the planform, they are at least competitive with the most basic stealth technology, though it appears they are still using stealth coatings rather than intrinsic fiber mats, so they are a step behind the F-35 in that respect. 

It is unclear whether this is a Air Dominance (F-22) or Multirole (F-35) fighter, or even if it is meant for the navy or air force. If it is air dominance, it might be a perfectly good plane, but will likely not be competitive with the F-22, which is a beast of plane. For starters, there is no indication of thrust vectoring, so the F-22 will probably be able to fly circles around the thing. 

It might be more successful as a multirole fighter –  it is impossible to tell without more information about specific weapon systems and mission systems. It does appear to have more external hardpoints for carrying ordinance then the F-35, but no gun pods. Also, externally carried weapons don’t help you if you need to be stealthy.

Compared to non-U.S. planes, the evaluation varies some. It is stealthier than the French Mirages and sexier looking than the current Russian fighter fleet, though the MiG and Sukhoi lines do perform quite well.

All in all, it looks like a very viable design. Only time will tell how it holds up