I've been using it for a couple years now. It's been a good experience, and it works completely as a keyboard. Customization is great, and there are a lot of implemented features thay have made it my go-to Android keyboard.
I switched from Gboard since I wanted to use an open source alternative for something as simple as a keyboard. It works fine as a basic keyboard, although its a bit unpolished otherwise. Swipe typing is buggy and there hasn't been many updates recently. I don't expect a ton from an open source keyboard to begin with, but this one provides a lot and could be even better if it starts being developed often again. It feels unfinished in its current state.
It used to have text suggestions, but now they are gone for me. Not sure what happened. I'd have to check again, but I'm not sure if they were taken out a while back or something.
Flawed, but it its awesome to have an open source keyboard with this much capability.