We started using Heroku very early in our journey and still rely on Heroku for database maintenance etc. Heroku's ease of use means we can operate with a much leaner team.
Superhuman has nailed AI integration into email. I love that I don't have to create meeting invites anymore. Superhuman's killing it with decent meeting names, zoom link included, correct attendees, correct duration etc. I also love the auto-drafted emails and auto-reminders. They're simple things that make a big difference.