I wouldn't group ALL China minis in the same group. Maybe all the cheap one's but there are some that are VERY near Honda CRF50 level of fit, finish and overall quality. Don't believe me? Call Service Honda and ask them what they think of Pit Viper MX bikes. If you are not familiar with Service Honda they hand build the CR500AF/AFX as well as the Junior X so I'm pretty sure they know a good quality piece when they see it. Not that these are the only top quality minis, there are a few others.

Parts are for sure an issue with most of the minis sold. Again not all companies are going to leave you hanging without parts support but a vast majority will. It pays to do a little research on what you plan to buy before deciding how good the deal really is.