I am impressed with Let's Encrypt reputation on the whole and as a Free ACME CA specifically.
Let's Encrypt never has given me any sense of being associated with "Snake oil", they are top tier.
Yes there are others as list in Free ACME CA feature comparison and I am not trying anything bad about them. It is good to have alternatives, and most seem to be working with the CA/Browser Forum.
While CAcert I have never found to have its root certificate in any Web Browser.
I am happy that Let's Encrypt puts in the honest effort to be a respected Certificate Authority and they are Free! 
Well done Let's Encrypt! Keep up the great work.
And Thank you to all the Let's Encrypt Staff.