I suspect integrating this has been the most requested feature for Virtualmin for the past several months (and we're about to roll it out, probably next week). For whatever reason, SSL is just always intimidating for people...even when it's been almost entirely automated, the back and forth between the CA and the server and dealing with private keys is a deal-breaker for a lot of non-technical users, so many of our users who are new to web server management have problems with SSL. It follows close behind DNS in terms of how much confusion it causes.
Anyway, I love that Mozilla and others took the initiative to pull this together, and used their not insignificant clout to push it to completion.
It does seem ridiculous that something like Let's Encrypt didn't happen sooner. But, now that it's finally here, I'm excited about it. I like that we can also expect mail to get more widespread encryption because of this, as well.