[rc4algorithm]

> For example you can no longer set the User Agent string on a per site basis natively in Firefox preferences [0].

This seems like a uselessly fine-grained control. I was surprised to hear that they ever supported it.

[userbinator]

Opera had this feature before it became yet-another-WebKit-clone. A lot of other settings were per-site too.

It's very useful for sites that complain or even block you from visiting depending on your browser, which you'll undoubtedly find if you venture far enough on the Internet.

[drdaeman]

uMatrix is relatively popular on AMO and it's about even more fine-grained control. ;)