Beyond the basics, a case can be made that Let's Encrypt is an answer to a social pain-point: Net Neutrality and internet privacy
. The Let's Encrypt price-point of $0.00 should accelerate us towards universal website encryption. In such a world, concerns about ISPs spying on and selling our web traffic data should be much reduced
There are many resources reviewing the pros and cons of Let's Encrypt (for e.g.). To add my 2 cents to the pile: the biggest drawback of the Let's Encrypt design, from my perspective, is that you cannot implement it on an intranet.
Meanwhile, I wholeheartedly embrace the Let's Encrypt requirement that certs be renewed every 90 days, because it improves the security of the encryption. I say we should renew the certificates with even greater frequency!