What makes a great customization experience?

Customization is one of the core focuses for 2017. We’ll be focusing on creating a great editing experience first, and then we’ll be extending that experience to encompass site building and customization. There’s a lot of work we can do to improve customization in WordPress leading up to the convergence with editing.
What do you think makes a great site building and customization experience? Outside of WordPress, what are your favorite tools and services for making sites? What makes them great?
Conversely, what are some of the biggest pain points you see within our existing customization experience?
If you’re interested in working on customization, please join us in Slack in #core-customize. The next meeting will be January 16, 2017 6:00:00 PM GMT. Looking forward to kicking of 2017!
Source: https://managewp.org/articles/14204/what-makes-a-great-customization-experience

source https://williechiu40.wordpress.com/2017/01/13/what-makes-a-great-customization-experience/