Letsencrypt is really awesome. I've used it in a few sites. All working good. In their recent update, they allows wildcard ssl too. All over Letsencrypt is production ready!
But I'm not using Letsencrypt nowadays
- I use Netlify for hosting static sites which gives me free SSL (they're powered by Letsencrypt)
- Our back-end (NodeJS) is deployed in Google App Engine in which Google provides free SSL
- I have a few WordPress sites hosted in DigitalOcean which needs SSL. I've set up Flexible SSL from CloudFlare. Even though it's not 100% end-to-end SSL (Client -> CloudFlare is SSL, not from CloudFlare -> Server) I'm pretty happy with it, very easy to set up.