I told our CEO that Buttondown is exactly the kind of scrappy startup we'd want representing our own startup.
If it's helpful for the HackerNews community, I've made my comparison spreadsheet free to view: https://docs.google.com/spreadsheets/d/1P9FyAYDdFZvTzmXVQi8A...
(I'm not an employee and have no financial incentive, I'm just a fan.)