I bought a Ness Big Sucker Stage I kit as well, and found the quality to be poor.
To begin with, I was unable to install it because one of the banjo bolts had poorly cut threads. Had I used the discrepant bolt, damage to the head would have resulted. I called the Ness tech line and, without hesitation, they agreed to send a replacement bolt, which will hopefully be here late this week or early next.
The quality of the backing plate seems generally poor. It is a cast aluminum part, and the one I received has a fairly high degree of porosity. Also, the interface between the breather tunnels and the air cleaner base plate lack any discernable fillet radii, which will locally result in high stress concentrations. Overall loading on the backing plate should be minimal but it is still subject to both thermal and vibratory loading, so it is possible that this area will develop cracking at some point.
The air filter itself is a K&N knock off which appears to be consistent in quality with the other components.
Unfortunately, I ordered this kit by mail order, and assumed that it would be of high quality since it has the Ness name attached to it. Had I seen the lack of quality firsthand prior to purchase, I would have decided against it and in favor of the SE kit.