My verdict: decent transactional API, but mixed reliability.
Brevo's transactional API does the job for confirmation emails, invoices, or notifications. The price is competitive and docs are clear.
What I like less: occasional bugs and variable stability are a real problem for transactional. When your password reset email doesn't arrive, it's critical. I've had desyncs and unexplained slowdowns.
My advice: acceptable if you already use Brevo for marketing and want to centralize. For critical transactional (order confirmation, password reset), Postmark or SendGrid are more reliable even if more expensive.