The quality of the bricks
Sets purchased were U18B NYC & U18B CSX. The quality of the bricks I found to be outstanding. I found on one of the motors a connection pin was broken but it didn't keep me from finishing the MOC build. The other set did not include the train wheels and couplers. I had few other issues with each set. As an experienced brick builder I found these few issues did not keep me from enjoying the sets. It did take a few attempts to access the instructions but that wasn't any major problem. The only other issue was how the MOC seemed overly complicated (while I understand this because of external details) it seemed that in places inside of the body that too many bricks were used and the ability to connect those bricks as one large subassembly was difficult.