The target audience for the newsletter was decided as "the busy exec". Not too much text, lots of gifs of functionality that we've built, etc.
There's some separate newsletters we do as well - there's a fortnightly "what's going on in the backend" one, curated by our infrastructure teams that's aimed at engineers.
Currently the general case newsletter goes to Engineering, Product, Product Design, and the exec group. We don't think it's quite good enough for the staff@ mailing list yet, but maybe we're just being over-cautious. It's really hard to get the balance right.