I've used it on both my previous phone (Fairphone 2) and now on the Fairphone 4. It's very painless, their installer is easy to use. The caveat here is that my most-used app is Firefox, and I don't use banking apps or Chromecast, which people seem to be worried about often.
I hope so too! The fallback is switching back to regular Android. If /e/OS doesn't work well enough for you, it wouldn't work well enough on other phones either, so in that sense this purchase isn't a waste.
