John Kerski has a baker’s dozen:
When I first started with Power Query, it was in Excel, through the Power Pivot feature. I was amazed at how I could transform data with just a few clicks and quickly create PivotTables. Then, when Power Query appeared in Power BI, I began working with larger data sources and more complex projects.
Through many trials and tribulations, I learned the capabilities of Power Query and the M language (the functional language that actually transforms our data), as well as its idiosyncrasies. Unsurprisingly, with Power BI adoption and rapid growth, many newcomers are learning the same lessons I did.
Read on for some of John’s early pain points. By the way, regarding John’s banker’s rounding note, that’s the norm for .NET, though not for Excel or SQL. It’s also more accurate in the aggregate than “to the 5’s” rounding, though it can be confusing to people who aren’t expecting it.