Ranked in these QuestionsQuestion Ranking
Pro Open source
The app is licensed under GPLv3 making it open source. This means that anyone can use the code and contribute. This also makes it easy to use on one's own server or for company solutions.
Pro Good security
After assigning a password to your account in Turtl, a key is created to encrypt the entire account. No data is stored on their servers meaning they have no access to unencrypted content. This is a huge leg up when comparing to other Evernote alternatives.
Con No iOS app
While many other operating systems have a client, iOS does not have one yet (though it is planned).