I have already done my part on my Mastodon account.
My main concern is the awful moderation of Meta's services. Bullying, celebration of loss of rights and violence committed towards of protected minorities; and outright misinformation are allowed. All while the very same people duped the moderation AI to flag any criticism of said hate speech as the real hate speech because false reportings. Facebook, instagram, etc. are notorious for letting big far-right accounts get away with hate speech and defamation, and I don't really think it'll be different on Threads for very long.
EDIT: In the meanwhile, I remembered screenshots of showing this exact moderation problem already happening on Threads, but to a way lesser degree, than on Facebook so far. Maybe this will make them getting booted from even the instances that didn't originally plan to defederate them.