June 2019
Framer X is a useful tool for building high-fidelity, working mock-ups. Probably the most comprehensive mock-ups of any available tool. You can:
I imagine that this last point is invaluable at a big company. Especially when changes are frequently made to the UI.
There are a lot of concepts to learn before you can get started with Framer X. Personally, I had to watch about 60mins of tutorials before feeling confident to create something very, very basic. This isn't unique to Framer, most tools in this category require a lot of initial effort before you can be productive (so if you've got something that works for you already - just stick with it).
For indie developers, it's important to be nimble and get MVPs out quickly. I think it's more efficient to use a lightweight solution for mock-ups and then move to code. Projects like Create React App / Expo give you hot module reloading on your devices so you can see your UI changes immediately.
Personally, I'm going to continue mocking-up with pen + paper (or Balsamiq for larger projects and Affinity designer for a few high-res screens), then going straight to code from there.
I can see myself trying out Framer X again in the future but it doesn't offer enough at the moment for me to learn yet another tool.