Use formatting from DAX Measure SSAS Tabular
Currently, if you use the Format() function in DAX for a measure in your tabular cube, the formatting does not get passed through to powerBI. ex Format(SUM(col1)/SUM(col2),"Percent") causes the measure to fail to appear in a report.
Lotta Carlsson commented
Minimum functionality in Power BI would be the same as in Excel.
You want people to use Power BI instead of Excel?
Coorporate users will not want Power BI, unless it can do all that Excel can and som more.
There's quite a few quirks with respect to formatting between SSAS, PBI and Excel - especially relating to time and duration values. It would be nice to see some consistency.
Please don't forget multidimensional cubes
Measure formats should also be passed through from multi dimensional cubes
Formatting appears correctly in Excel and other connectors, but not in PowerBI