HAve not mastered it at all yet.
It is a mechanical machine that only sews straight, but it does so very fast.
It needs a lot of oil - regularly!
It takes a bit to get the sweet spot between tension and speed.
Mine likes to have the thread go thru only 2 of the tension holes but that is just me.
I've heard that it is unhappy with some threads.
It takes a special needle.
There is a tool that helps guide the bobbin in the slot.
It does not drop the feed dogs - uses a cover plate instead.
There is a yahoo group online for the GQ.