After applying to join the Let's Encrypt beta program a while back, I got an email with an invite for the domains I registered.
Yesterday I set it up, using the '--standalone' mode of the letsencrypt-auto program - so I had to close down the webserver while it ran - and configured Apache to use the certificate obtained.
Very nice, and very nice job by the people working on Let's Encrypt!
I missed a good handful of my (sub)domains, so I have applied for those, and I am planning to get a certificate for use by my mail server, and one for my XMPP server next.
And then I need to automate the renewal of certificates - Let's Encrypt have chosen than certificates are valid for 90 days, making the downside of a security breach relatively small, while also encouraging people to automate the process.