I don't have any firm opinions yet. I definitely feel the knee-jerk temptation to not federate with them, but on the other hand I guess federated Facebook products is pretty much what I want from them.
I don't care about Threads very much (at least yet), but I know a lot of people where my only way to get in contact with them is Facebook Messenger. So if I could contact them without needing to have a facebook account myself, I'd be quite happy.