This is great news. Furthering HTTPS adoption is the best way we have to combat pervasive surveillance, and we're making steps in the right direction before HTTP2's opportunistic encryption [1] will improve things on an even wider scale.
We'll also face some new challenges. Over the years, many users have learned to "look for the padlock" before entering their passwords. More sites moving to HTTPS will also increase the percentage of phishing/attack sites served over encrypted connections -- with the padlock to match. We'll need to renew our focus on training users to check for the correct domain name (and possibly an EV cert), or phishing sites with a cert from Let's Encrypt will become a real threat. Browsers are moving in the right direction, displaying https less conspicuously than before, and emphasizing connections with EV certs.
We'll also face some new challenges. Over the years, many users have learned to "look for the padlock" before entering their passwords. More sites moving to HTTPS will also increase the percentage of phishing/attack sites served over encrypted connections -- with the padlock to match. We'll need to renew our focus on training users to check for the correct domain name (and possibly an EV cert), or phishing sites with a cert from Let's Encrypt will become a real threat. Browsers are moving in the right direction, displaying https less conspicuously than before, and emphasizing connections with EV certs.
[1] http://httpwg.org/http-extensions/draft-ietf-httpbis-http2-e...