I've found need for a note taking mobile app recently, but after trying to use Keep and seeing that it has zero organizational tools such as tags or folders, I just started to use Evernote instead.

Frankly, it is nearly impossible to recommend Keep when Evernote exists. Until they have, at minimum, some way to organize notes, it's just a pile of notes sitting in one window. But it would still be a hard sell when compared to all the Evernote features, such as the desktop clients that allow you to take screenshots and annotate them.

Edit: Oh, and there's also Geeknote¹ for CLI usage, as well as Vim plugins².

¹ http://www.geeknote.me/ ² https://github.com/neilagabriel/vim-geeknote

I never really use it for anything important anyway but I can't imagine it going anywhere other than getting rolled into some aspect of Drive. It's already sort of a simplified note-centric version of Google Docs and mostly works the same way. I just use it since it's easy to keep on my phone's home screen for quick notes and snapshots I want to be able to access elsewhere if needed. I know something like Evernote is more fully featured but since Keep came out, I don't really use Evernote anymore. I think my needs in that space are just simple.

The chances of it being "gone" tomorrow are basically zero. The worst thing that could happen tomorrow would be an announcement that in 60 days, no new Keep items could be added, and you'll have a year to download all your old ones as text, HTML, or JSON.