It would be nice if you could describe a dependency from one project version to another. A good example of this is a complex web application. The web application likely has a JIRA project of it's own. It may have several components that are also setup as JIRA projects. Using the component section of a project isn't always useful as the component details vary from the project details and the component might be shared among projects.
In any case, you could then associate Component 1.x.x as a dependency to Project 1.x.x.
This would be very useful when trying to see a summary view of all oustanding issues for an end product.
Our current workaround is to create an issue in Project 1.x.x that is called "Integrate Component 1.x.x". You can then link this issue all of the Component 1.x.x issues. As you can imagine, this can be time consuming.