Simplenote is a great basic note-taking app. Sometimes the more full-featured note-taking apps are more hassle than they're worth when you just need to jot down a quick idea.
The markdown support is particularly nice, allowing for quick and easy formatting when you do need it.
The notes quickly sync across mobile apps and the web app, which means your notes are available when you need them. I've used this app for a few years now and it's my go-to note app.
After using Apple Note, OneNote, Evernote, SimpleNote ends up to be my default note app, despite (or maybe *because of*) its seemingly lacking of advanced features.
