First of all many thanks to all at letsencrypt, this is a huge leap forward for open source and free software.
I have a working letsencrypt certificate on my site.
The certbot docs imply that apache versions greater than 2.4.8 will accept a combined certificate and key file. I am running apache 2.4.10 on a debian jessie server and tried the single file approach, but it failed. I replaced the single SSLCertificateFile pointing to fullchain.pem with separate SSLCertificateFile and SSLCertificateKeyFile pointing to cert.pem and privkey.pem and all was well.
Has anyone else had a similar experience?