History tells me that I'm a very finicky note-taker. I've purchased and used a large number of note taking systems over the years. Voodoopad, Evernote, Notational Velocity, Simplenote, Bear, Trello and Tiddlywiki are a few of the tools that got more use than others. I really enjoy the wiki style tools where I can link in-between notes. Tiddlywiki would be my favorite if it had a good offline client. I really enjoy the UI/UX of Bear, but it's not cross-platform enough. Notational Velocity is a little too offline. I really like Trello's features, but the UI bugs me. And none of those (except for tiddlywiki) has trust-no-one encryption.
I recently started using Standard Notes, which isn't perfect, but has a couple of qualities that mean I will probably continue to use it in addition to other
Your notes are encrypted and secured so only you can decrypt them. No one but you can read your notes (not even us).
That means I don't have to worry too much about what sort of notes I drop in there I can feel relatively good about them staying private (note: I haven't done enough vetting to know if they tech is trustworthy, but their intent is in the right place). Private by default is my default.
If you've every used simplenote or notational velocity you'll be familiar with the design of Standard Notes. It's a tagged set notes that are easily searchable and primarily plaintext. The system allows for some useful markdown viewing and other richtext style notes if you've paid (which if you're using it you should consider doing). My experience so far is that because it's designed as a premium feature the advanced editors feel a little tacked on and the experience between the different platforms is not 100% consistant, so sticking with the simplest editors is the best option. It does have clients for iOS and Linux, which at this point is the platforms I care about (it has others too).
When I started, I imported my simplenotes, which, in retrospect, was a mistake, because I had a whole lot of crap in there. I've started getting some tags in there to help me get the current set of info organzied, and I'll be migrating some other notes in there over time. It's definitely going to be my default location for text that needs to get saved and synced to all my platforms. Basically its just better than simplenote because of the base encryption that it does (which really was my primary complaint about simplenote).
The big reasons I'll still need to use something else are: collaboration and wiki-style complex notes. There is no notion of sharing or collaboration for Standard Notes, which is fine, it's very very difficult to get encryption and sharing done in the same app and not have big problems. Have a rich, wiki-style, note linking system would be great, and it's on their radar, but I'll have to keep using Trello or Tiddlywiki for that sort of thing for the forseeable future. I've been having fun automating my own stuff lately, so maybe I'll set up a hosted tiddlywiki.