[Chilinot]

Is it really a single point of failure though? Certificates are renewed well in advance, and there are several free alternatives with ACME support to LetsEncrypt today.

Switching to a new provider in case LetsEncrypt goes down is as simple as updating your scripts.

[iso1210]

A large number of sites use LE, and only LE.

Perhaps this move will mean people actually update their scripts and get it working on another system

[gsich]

Why? If you only renew at the last day you will run into troubles independently of Lets Encrypt.