Has some really nice features, such as pinning, tags, and markers next to the scrollbar to show note positions, but a bit glitchy, so still needs some improvements. Another reviewer mentioned that it pastes what's in the clipboard into the note when resizing it, so I tested that out, and I find similar behavior, but not quite as they described. It's not doing it every time, but most times, and it's not pasting what's in the clipboard, but rather "moz-extension://47d7522b-6186-4883-a143-5af081a16cc8/img/resizeCorner.gif" (without the quotes). Also, when the page is focused (click on the page outside of the note) then I try to select that text, the selection "breaks." First it was keeping the first few characters on each line selected, then the next several would be unselected, then the rest would be selected, and now it's keeping the first four on each line selected and the rest are unselected. I also had a note jump from the middle of the page to the bottom, where it stayed for a few seconds before jumping back to the middle. This happened shortly after pinning it and then scrolling. And finally, enabling "advanced features" doesn't appear to do anything.
If these issues are fixed, and if the ability to set a default position (I like to always have new notes open in the top-right corner by default) and size are added, this would easily be a 4+ star addon. If Internotes notes could be imported and if there could either be an option to make left-clicking the icon create a new note instead of opening the popup menu and make the menu accessible either via the right-click menu or by clicking the icon with a modifier, or else just adding a second icon/button to create a new note, it would be 5-stars for sure (if syncing isn't important to you, since it seems there's issues with that). I'll definitely be watching this one, since I'm in desperate need of a replacement for Internotes.