data is removed in rc1 release from Route. The remaining options currently are query strings and route parameters. Both of which visibly add values to URLs. There are many scenarios for which the user doesn't need to see passed values as part of URL, and that makes URLs user friendly while the functionality remains the same. Currently to pass an arbitrary value from one component to another without appending it to URL, a data service or a mediator is required. Either of two are an added complexity if the arbitrary value is a simple token of some sort.

I suggest bringing back the data as well as adding an optional Boolean value to router.navigate which specifies if passed values are supposed to be added to URL. If false then pass them behind the scene and if true do as what happens currently (query string or route param).