I understand your concerns, it's normal, we are talking about a lot of money. I had 2 orders with GON and both were delivered, and those boards are the best boards I ever had and I will never sell them.
In many ways GON is a pioneer, he is the first Korean keyboard builder, as far as I know, who opened to the "western" keyboard community. There were times when getting a Korean board was close to impossible, not to mention a custom build. You had to have connections and pay top dollar to get one, and the waiting time was huge.
I think this time GON was a little overconfident in his ability to take so many orders, but he will deliver, and when you will get your board you will see why it was worth waiting.
If you want to "buy" some peace of mind, bite the bullet and phone him, or try to call him via skype, he is a really nice guy
If you want to get a glimpse at the amount of work involved in a custom build watch his videos, his hand soldering skills are perfect, I've seen boards machine soldered that are far away from his boards.
One thing I learned in this hobby is that you need a lot of patience if you want something special, caps, boards, cases... It's an expensive hobby and requires a lot of patience. If you accept these things you have only nice surprises
For instant delivery you get only standard, non programmable (truly programmable) boards and cheap caps.. I could never go back to that