I have been experiencing issues when refreshing the data. Any refresh option of a dataset, or a dataflow, either manual or scheduled, takes unusually long time.
Even after successful refresh the changes in the source are not propagated to the Service.
For example: I use a .pbix file as that I publish to a Workspace. After I add some measures or change some data in the .pbix (stored locally) I refresh the resulting Dataset in the Service but the Report built on top of it doesn't reflect any changes.
The same holds true when using Dataflows and a Gateway.
The only way to reflect chanes is to republish the .pbix, but this resets any reports and dashboards that were built on top of these sources.