For those asking themselves what's the difference between this and other editor-in-widget plugins out there, like BlackStudio TinyMCE, I took it for a quick test drive. There are two main differences I could see:

1. The BlackStudio TinyMCE editor appears in a panel on the left beside the widget in the customizer. The updates are still automatic (no refresh required), but there is a distinction between the editor where you type and the content block where your type appears on the live preview. By contrast, Note has no separate editor. You type straight into the content block on the live preview. It is a more immediate experience but can be a bit disorienting depending on your expectations in the customizer.

2. Note is not a full HTML editor. It offers a small subset of markup options (just those in the screenshot above). I can see that being useful for client projects, where I don't want them to go crazy. But having the full TinyMCE editor, including the Add Media button, is also pretty useful.

At first glance, I wasn't sure why this warranted a post on WP Tavern. But now I can see how the streamlined UX approach Note is working towards has something unique to offer for editing small snippets. The only real barrier I had was figuring out how to find the markup buttons when typing. Perhaps they could implement a similar approach as the Focus v2 feature coming in 4.1 and display the markup options when the mouse goes hunting.