Using both actually. For commercial projects, paid certificates, I've had too many cases of the certificate stop working in Chrome with an HSTS Error and the 3 months things is not great, typically I buy certificates to last for two years at least.
For personal / non-commercial projects, LetsEncrypt is fine.
Corporate environment? Paid CAs.
Hobby project? Let's Encrypt. Though I am still using my old StartSSL certificate until it hits its end of life
Mail/Code cert? Looking for a new one. I am still using my old StartSSL cert, but they have issues at the moment....
This is definitely a no-brainer. LetsEncrypt is free, backed by google and has the same level of security as other, Paid for, CA's. Especially for startups - this is a god send!
Rajkumar
Fullstack Developer.
As others already mentioned, for all my freelancing(tight budget) and hobby projects, I use LetsEncrypt(Started using recently) and at office, they are on their own and so mostly Paid CAs. Can't do much.