First up - I'll point out that I am a distributor of them.
Now for the answer. I was one of their earliest distributors so I have seen the evolution of the engines to what they are now. The official distributor network is very strong - we often talk to each other and assist each other as required with information, tech support etc.
The distributors have spent a lot of time working with the factory to provide feedback on suggested improvements as well as the writing of manuals etc. A lot of that feedback has also been provided by customers. The factory is a factory that listens to what the market requires and it has acted accordingly. - that is what has made the engines what they are today - well designed and well built powerful units at quite a reasonable cost.

I have at least one of each engine mounted in an airframe and we fly the heck out of them - we also let prospective customers try those airframes out (we sell airframes as well - so that is a win-win for us). My oldest one has over 280 hours on it without a strip down - it is an early version 45cc. I also have a 50cc that had over 130 hours running time with 100:1 Belray SC1 oil in it - just to see how tough they are. I stripped it down after then because we were getting bored with it and the internal "damage" form running it to lean on oil was minimal.

There was a stage recently where another company was claiming to be selling RCGF engines - that particular company has previously had an awful reputation in the marketplace but the engines they were selling were most definitely not RCGF engines - they just happened to be made in the same province. There was also a company that purchased a stock of very old versions of the engines for sale in the domestic Chinese market. Those particular engines had not been through the normal QC process as the design had been upgraded on them prior to them being sold and they were not meant for release to the international market as they were sold without warranty. The company that purchased them then promptly sold them world wide with no warranty support or technical support. Fortunately, the factory still backed those engines with warranty for the unfortunate customers that received them but the customers did need to send them to China for that to happen.

So - in summary, they are strong engines that are well designed and manufactured with a great dealer support network (We all strive to continually improve that too) all at a reasonable price.