Thank you so much for some insights. I generally develop this extension in a vacuum and to get some perspective is very helpful.

That being said, a few things you mention have been considered or compromised on mainly in the name of asking for too many permissions, which is why I only use the small favicons instead of bigger icons. I like your idea of adding the search bar into the extension and I'll keep that in mind in the versions ahead. As for the preferences being a toolbar icon, this is due to cross compatibility with Chrome although I'll review my options for Firefox.

In regards to pre-loading, it actually is preloading up to 15 more APOD's on first load in anticipation of a user clicking the random button a few times. If you try this you should see that the subsequent APOD's load very quickly, though this is for naught if you are opening and navigating away quickly. I'll see what I can do in regards to locally caching the "Today" APOD and other images.

The Google analytics is performed according to Mozilla's standards which forego the use of the usual GA.js CDN script tag. The tracking from Mozilla and Chrome are both exceptionally minimal and Google analytics will remain for the time being.

Anyway, thank you again for some insights and after a refactor version or two I will get back to feature mode and do my best to integrate in some of your suggestions!