We use TypeScript and at first it seems like a burden, but pays off after a while. We used to have a problem with CSS - every time we had to implement some new UI, we just ended writing stronger selectors to override the parts that felt would break if we refactored them. CSS modules solves that problem for us. It's nice that we are allowed to use flexbox. The biggest problems for us are that <video> events are not being dispatched properly or scaling problems when keyboard appears.