The upper is certainly more robust (thicker and heavier) than your typical receiver and is machined exceptionally well. Aside from this notable difference, the quality and tolerances of all other parts on my upper seem to be right there with any other entry-level company’s products. I also get sub-moa accuracy with my particular 350 legend upper. They are most definitely standard, mil-spec level components, but not at all sub-par quality. You are getting what you pay for, without the mark-up as most companies do on entry-level rifles. Overall, I am happy with my upper from them, and it was certainly worth the price.
All that being said, I would still go with a PSA upper if they had a side charger to choose between. It’s hard to beat anything PSA made for the price.