Something I noticed in Edge - on its addons site, you can click "Get" on multiple addons quickly. It's even aware of addons you've already installed!
Compare this with Firefox, where you have to drill deeper into each page to install it (or open each in a new tab). It's also possible to unknowingly try to install something that you've got installed already:
These small touches would really uplift AMO. I'm also probably not alone in having to try out a few different addons before finding one that works well - then I remove the others later.