It would be extremely helpful if we could query across object relationships, similar to the functionality supported in the Export ZOQL. For example, if we want to pull Account information for a Subscription, we need to perform a query to retrieve the "AccountId" from the Subscription and then a second query to retrieve the information from the Account. It would be fantastic to be able to combine this into a single query like "Select Id, Account.Name From Subscription".
In this scenario, performing 2 queries is not extremely costly. However, there are several other scenarios resulting in far more sequential queries (such as retrieving charge level details for a Subscription, or Account level details for charges, etc).