There’s like… no downside: all upside.
Edit: I exaggerated, of course. Below this are some downsides that individuals have experienced. But personally, my experience using Firefox on desktop for Mac has been all upside. If everybody who can just tries it out, you might be surprised at how friction-free the change is.
Sitting in the splash zone of this whole thing, Matt’s contribution to the project is a net negative. Professionally and personally, he is seems unable or unwilling to deescalate conflict. In fact, he creates conflict where none is necessary, and then seems to act shocked and disappointed at the results.
He makes decisions unilaterally that don’t reflect what a thoughtful steward of an open source project would do. (And I say this as a proponent of the idea of the block editor, and as someone for whole building sites with blocks is my bread and butter- except I use ACF, full disclosure.) an example, picayune as it may seem, is the function capital_P_dangit().
It’s not picayune, by the way.
And now this mess. This is by far the most destructive thing he’s done. He needs to be removed.