nvALT syncs with Dropbox and is free.

I've used it for years and hasn't been a problem with syncing between my devices (Android phones, Macbook Pro).

The tradeoff is the elegance of Evernote's many robust features in favour for simple text files. I love how it streamlines the writing experience into a vertical line. It's as simple as it gets next to Notepad.

Initially, I used it as a dump for anything but found a way to take down notes and organize it to my accord. The Verge does a good job explaining how they use it for idea-jotting when you're on the go.

You can read more about it the original NV.