All right, in brief, here’s my take.
I can only speak for myself. I’m not one to panic easily, or so I hope, much less over a messaging app. I’ve read up about the announced changes to the terms. In particular, I’m aware of the business aspects of the endeavour. I also know about the continuing end-to-end encryption of individual WhatsApp chats.
My lingering general concern is, WhatsApp is Facebook, and as the public had to learn the hard way, Facebook lies. When Facebook acquired WhatsApp, they swore not to do certain things with the app, only to implement them anyway a few years later. If I counted correctly, this is the third iteration of this behaviour. It’s a pattern.
I use messaging for sensitive communication (lawyering, arbitration, mediation). Not because I want to, mind – as far as I’m concerned, we could stick to end-to-end-encrypted e‑mail forever. In any case, I don’t want Facebook or WhatsApp to milk even only the metadata of these communications. When asked, nor do my clients or others I communicate with. Not to mention the risk of third parties accessing such metadata or other personal data, which has happened in the past, with or without Facebook’s knowledge.
Overall, I feel WhatsApp no longer deserves the trust I’ve had in it for a few years, since I went back to using it after they introduced end-to-end encryption. Signal (and, with some restrictions, Telegram), here I am!