Works, but if you look at the GitHub there are issues. It's kinda sorta maintained, but don't expect to do any calling. However, it's more than suitable if you need a basic desktop client for Messenger.
It is working well now. There are no delays. I have had worse experience with windows app-store version ;)
I don't know how well it handles audio or video calls because I haven't used it for those. It's great for text and images - nice alternative to a browser/app.
It's completely useless in recent times. During a call the screen after a few seconds goes completely white, the other party's voice is lost, the program does not respond to anything.