>Chrome's reviewal process is really nice. It usually takes <30 minutes.
Nice for the extension developer, but there's a reason for Mozilla's longer review process. They actually sit down human beings to look over the code and that makes all the difference in keeping AMO clean from malware.
Case in point, a recent phishing attack on Chrome extension developers: https://arstechnica.com/information-technology/2017/08/after...
https://github.com/mozilla/webextension-polyfill
The biggest challenge for me was addressing browser incompatibilities and Firefox bugs. This is a big one:
https://bugzilla.mozilla.org/show_bug.cgi?id=1193394
Another is that Firefox doesn't fire blur events when DOM elements are removed or hidden.
The Firefox approval process is slow. Mine took 3 months the first time, < 10 days the second time, and this third time it's taking over a month.
Chrome's reviewal process is really nice. It usually takes <30 minutes.