Completely overridden by the standard issue US English that cannot and will not let me replace it with the correct English for my locale, UK.

ca ne marche pas

Says it's installed but it simply doesn't work. Spell check still marks UK spellings as wrong.

no matter WHAT i do, firefox ALWAYS resorts to USA spelling.

Quite incomplete but better than anything else free out there & I appreciate this author's maintenance over the years.

Doesn't work. I can write any spelling at all on Twitter and it does nothing.

It do nothing. I have installed the English pack and I still only have the Swedish dictionary.

There have been a few instances where certain forms of a word are detected as false positives, but those are low enough to not be inconvenient. (I have only experienced the dictionary part of it - in case there is more to it)