What are the biggest mistakes with getting started in Datasets?

One thing worth trying with What are the biggest mistakes with getting started in Datasets? is a controlled comparison around getting and started. Use the same input for each test and note what changes in the output rather than judging from a single run. The original point — "I am trying to improve my approach to Datasets and could use some practical advice. I am particularly interested in getting started and productivity. I would like to compare appro…" — gives a useful starting point for that comparison.

For What are the biggest mistakes with getting started in Datasets?, I would separate the problem into setup, output quality and repeatability. getting and started fits into that because it can change the result quite a lot depending on the workflow. That should make it easier to tell whether the change is actually helping.