It would be nice to see how long a report took to run in (a) the "Report Runs" pane of the portal, (b) the run history for each report, and (c) in Excel itself, when run through Cosmos -> Authoring -> Preview.
It would also be nice to see the date and time a report was run, in the run history, instead of just the report options that were used.
Thanks!
In the new Portal which will be released 8/25 you will be able to see all of your runs for the report along with how long each one took. There will also be a graph plotting this visually.
Admins will also be able to go into an Admin Portal to see reports run for all users along with when they ran and how it took.