I started using Polars for the "rapid iteration" usecase you describe, in notebooks and such, and haven't looked back — there are a few ergonomic wrinkles that I mostly attribute to the newness of the library, but I found that polars forces me to structure my thought process and ask myself "what am I actually trying to do here?".

I find I basically never write myself into a corner with initially expedient but ultimately awkward data structures like I often did with pandas, the expression API makes the semantics a lot clearer, and I don't have to "guess" the API nearly as much.

So even for this usecase, I would recommend trying out polars for anyone reading this and seeing how it feels after the initial learning phase is over.