Hi Peter,
yes, and no.
It's been possible to get free certificates for some time now from StartSSL.com - however they have some restrictions on what you can use the certificate for. Plus, like with LetsEncrypt they're only free for DV certificates.
DV - Domain Validation - prove only that you have "control" of the domain. That's good enough for most of us, but if I say register googlehelp.com I ergo have control of the domain and hence getting a DV certificate is easy.
EV - Extended Validation - certificates go to the next step and prove that you are entitled to the "brand" in the domain. So google gets an EV for googlehelp, but you and I likely can't.
EV certificates are the ones that go Green in your browser, so are a big deal for companies etc.
LetsEncrypt though certainly makes it a _lot_ easier to get a certificate and install it, especially if you are running on Linux (for now). Don't get me wrong, free certificates are a good thing, but this isn't new.
cheers
Bruce