Good question. Some are interesting, some are just useful. For SQL DW doing something like using Event Hubs Capture feature to trigger ETL into DW is really useful. And generally interesting. For Any datastore (SQL, CosmosDb, others) being notified of create, update, or delete operations is also useful and interesting. I think broadly speaking the three areas where Event Grid will be very interesting are for
Serverless: tie your serverless functions together with Grid.
Operations: make rich provisioning and deployment or scale experiences.
Enterprise integration: use workflow and orchestration services like Logic Apps to perform integration across cloud services, cloud providers, and on-premises.
Finally, the custom topics stuff really makes not just serverless, but any cloud application have some interesting possibilities for event and data distribution and publication.
Serverless: tie your serverless functions together with Grid.
Operations: make rich provisioning and deployment or scale experiences.
Enterprise integration: use workflow and orchestration services like Logic Apps to perform integration across cloud services, cloud providers, and on-premises.
Finally, the custom topics stuff really makes not just serverless, but any cloud application have some interesting possibilities for event and data distribution and publication.