As you can see above, this add-on will introduce a nice, pleasing grey screen (which I like a lot more than black screens), change the text colors, and, unfortunately, remove much of the page content. Due to how this add-on functions and what it wants to do, this is necessary.
I've messed around with this add-on for maybe a week or something now, and on most of the sites I have tried it with I am missing a lot of things such as inlaid images, borders, and other assorted elements. This isn't a huge deal most of the time. It just makes pages look crappy. But, several sites also lose certain functionality when buttons or other interactive items go missing (not necessarily removed, just invisible). Then you have to swap back and forth between blinding white and pleasant grey, and that isn't such a happy thing.
Your eyes will love this. But people who want to retain full functionality of their webpages with a permanent eye-saving solution should look into much more in-depth alternatives such as Stylish, F.lux, and Turn Off the Lights. There are many advanced night mode extensions (such as Night Mode Pro or Night Mode Eye Guard) that I would actually recommend Owl over, because both of those absolutely butcher pages, even if they try to keep many elements.
Three stars for basic function and appeal. Doesn't really have any options and leaves a lot of the page out in favor of easy reading.
EDIT: I can't really reply as far as I know and I don't want to spam with another review so I will hope you see this. A couple of these already have dark themes, but your extension stays on throughout the entire session so from time to time I would have to toggle it myself. For testing I am just checking websites I go to that are relatively popular.
some websites that lose interactive elements,
- Outlook Mail (Many icons on the top bar as well as the tick boxes)
- Imgur (Some icons on the top bar and the upload buttons)
- Photobucket (All image thumbnails)
- Netflix (All tile thumbnails)
- Pocket/getpocket.com (Loses most buttons on the top bar and above your pocket list, as well as thumbnails and page titles)
- DeviantArt (Loses all image thumbnails on front page, searching is fine though)
- YouTube loses its video player buttons.
Some additional features I think would improve this add-on
- An option to toggle Owl for the entire session (like currently) or to only activate it per tab
- Option to permanantly activate/deactivate Owl on a specific website
- Maybe a shade selector for people who prefer something lighter/darker. I think this grey is perfect though.