> effectful and Bluefin are here to stay. I guarantee it. For non-IO-based effect systems (e.g. polysemy, freer-effects) I agree.

Just to be clear I think Bluefin is really cool and I'm a fan of your work overall.

I'm speaking from the industry/production perspective here. When polysemy and freer-effects were released there was a similar belief that they were here to stay.

transformers and MTL have stood the test of time, are heavily documented, and are pervasive throughout Hackage. Understanding them and how to build programs with them is essential for anyone trying to break into 'production haskell' as a career move.