I have a custom Serotta and it is so beautiful and such a joy to ride. Besides fit Serotta did a great job of building it proportionally. I'm 5'1" and have short arms so I needed a very long headtube. Because the headtube needed to be long compared to my Standover height I thought my bike would turn out to be a sloper, like a lot of the WSD frames. However, Serotta was able to build the bike to my needs without an extreme slope of the top tube. The slope is only 1 degree!
Btw, the fun of building your own bike is that you chose the level of components that you want, not what some company thinks you need.
A good custom fitter can work with your physical needs to build a frame for you.
Here's pics of my Serotta