I sometimes like to decide or make alterations in the browser based on ideas, sketches and thoughts but I would be cautious about saying I 'design' in the browser.

I think design as a term is too broad and takes in to consideration too many factors to be able to say that we actually design 100% in the browser. I feel the browser is just one more tool we can use to turn design ideas and thoughts into shippable products.

The only current way to share symbol libraries is to save the file with the symbol library as a template file and share that with your team members who can then open new sketch files from the template.

Our work around at the moment is to have a centralised file on a git repo which can be updated by any team member. Its not ideal but it kinda works.