ACME support in ACM is the kind of thing that should have existed years ago. Any tool in the ACME ecosystem — certbot, acme.sh, step-ca clients — can now talk directly to ACM for public certificate issuance and renewal. No more maintaining bespoke Lambda renewal pipelines or routing through Let's Encrypt when you're already on AWS. This matters most for teams running hybrid or multi-cloud setups where certificate tooling needs to work the same way regardless of which issuer is on the other end. Standardizing on ACME means one automation path everywhere.