It's tethered to your phone, ugly, and feels a lot like an afterthought. Last I checked, it also doesn't work with the iOS version of Signal, so if you use an iPhone you don't get any desktop support at all.
In short, it needs a lot of work before it'll be usable for anybody in a similar position to myself.
Compare that to Wire, which has much more convenient multi-device support, but accomplishes that at the expense of keeping the entire active graph of communicating Wire users in plaintext in their servers on AWS.
Both Wire and WhatsApp (which have comparable security models with some marginal tradeoffs --- WhatsApp metadata is in Facebook's custody, which is not great, but Wire doesn't have Facebook's extremely competent and well-resourced security team) are reasonable choices for secure messengers.
Telegram is not.
I might if either of those had proper desktop clients (they don't). I spend most of my day sitting in front of a computer, so chat apps that offer only wonky web app "phone bridges" for desktop users don't make much sense for me.
The best part of iMessage and Telegram is that their desktop clients are as capable as their mobile clients, and they're real independent clients. Until WhatsApp and Signal offer that, I have little interest in them. Maybe the majority of the internet connected world conducts their communication primarily through a smartphone, but that's not me.