I would definitely add practicing design/UX/etc. to #1.

A big part of creating a high-quality product is about good presentation & interaction - even if you have a designer in your future team it helps to speak their language.

Previous HN threads on design: http://news.ycombinator.com/item?id=1604915 http://news.ycombinator.com/item?id=1103578 http://news.ycombinator.com/item?id=1474315