I recently switched to letsencrypt for some of my side projects. It works, but there are pitfalls.

The official client didn't work for me at all (crashed with an error message every time), and there is little documentation to help you out. However, the Ruby client works, so I'm using that. For some reason though the Ruby client was stuck in development mode leading to invalid certificates being generated without warning - I had to manually edit the gem file in order to circumvent that.

Once it's running though, it's very cool. I'm going to start using it for client projects in the future.