I think this is going to be a really good service: the service can be used easily with Workers making it super easy to not only send transactional emails but use it for forms embedded in Pages. I am very much looking forward to using this.

However, I still think AWS SES is the gold standard of deliverability because of their constant monitoring of your reputation (bounces etc). I always combine it with SendOps (https://sendops.dev/) for easy setup and deep analytics to avoid those issues.