Black boxes are mass-produced. How many CMOSS batteries died prematurely in Dells ? How about the recall for capacitors in Dell GX280s that popped ? As long as a white box is built with quality parts you are fine. I build my own machines three of which are running the latest MS Servers. I have one machine that is 11 years old (soon to be replaced) that has never been even re-imaged.

A white box can be built to your exacting specifications. A white box can be a higher-end build than what you would normally get from a major manufacturer. You look at even the power supply of a HP dc5800 or dc6000 (business class computers) and they only have a 300 Watt power supply. That's fine for most cases cutting it close for higher-end needs. You can argue that there are indeed more headaches and you have to engineer your own system build. Is the quality of a black box acceptable ? Yes. It is definitely convenient.