I don't recall any issues with the actual build problems that change over time. It is likely there will be bugs fixed over time with firmware and software.
I know back in my Phantom flying days, things actually went the wrong direction. They released 3 different versions of the Phantom 3 advance/pro controller, and the 3rd version had less power and some people saw a difference in range (although some tests didn't really show much difference). So, they could make a change to fix problems, or you run into them making a change for some other reason (like to a cheaper supplier). You get a warranty, so I wouldn't worry too much about buying early. On the other hand, waiting gives you a chance to see what real world good and bad there is outside the reviews and let the firmware catch up.