They've been interating on the construction process with each one built. I've been welding (DIY) for 30 years, and the first ones looked pretty bad to me - lots of distortion, and I actually thought the first one was just a mock-up. But the process is clearly improving with each build. I still think the nose cone looks like it will improve in the future, as it doesn't look as precise as the main body is now looking, but I'm sure they're working on it.
This, overall, is an amazing achievement. I watch every F9 landing that I can, and it never ceases to amaze me. The FH two-booster landing looked like straight out of a SciFi movie. But this... this is next level again. The 20km flight will be truly incredible.