Gathering data from Certificate Transparency logs, here's a snapshot in time of Let's Encrypt's certificate issuance rate per minute from 15-21 January 2016. On 20 January, DreamHost announced formal support for Let's Encrypt, which happens to coincide with a nice rate increase.

Note: This is mostly an experimental post with embedding charts; I've more data in the queue.

Let's Encrypt Issuance Rate per Minute, 15-21 Jan 2016

note: timestamps are GMT-7