Is Refresh button in the Office 365 (cloud) Power BI report intended to refresh SharePoint Lists?

Hi isaksp00,

• here is no way to cause a dataset in the Power BI Service based on Sharepoint Lists to be refreshed on-demand (manually).
• the only way to refresh the dataset is by setting up a schedule, limited to max 8 per day and limited to every hour or half hour (approximate, as the service seems to refresh some minutes after the scheduled time).

We can manually refresh the dataset via Refresh Now.

• you must click the refresh button on the report page to cause the visuals to reflect the new data in the dataset, after a dataset refresh. In other words, the visuals will show old data when you open a report after a scheduled refresh if you do not click refresh.

Nope. If you already open the report and leave the report here, then make the dataset is refreshed successfully, at this time you need to click Refresh or refresh the report page to let the data updated in visuals. If you open the report after the dataset is refreshed successfully, the data will update in visuals without clicking Refresh. 

• Is there any sort of service level for the actual data refresh maximum "lag" for a scheduled dataset refresh? In other words, is there a maximum amount of time after each schedule event that the refresh will occur?

When you configure a time for scheduled refresh, there can be a delay of up to one hour before it begins. See: https://powerbi.microsoft.com/en-us/documentation/powerbi-refresh-data/#what-can-be-refreshed 

Scheduled refresh for imported datasets timeout after two hours. This timeout is increased to five hours for datasets in Premium workspaces. If you are encountering this limit, you can consider reducing the size or complexity of your dataset, or consider breaking the dataset into smaller pieces. See: https://powerbi.microsoft.com/en-us/documentation/powerbi-refresh-troubleshooting-refresh-scenarios/#scheduled-refresh-timeout 

Best Regards,
Qiuyun Yu