Bug 134740 [Wizards] PDE product wizard is not obvious to use.
see attached image. The wizard for creating a new product opens with a file name initialized to ".product" which is selected. Generally this would imply that this is a good default but if you start typing you will replace the text with something else that is also a good name. If you require an extension for a file you should add it yourself like the "Export Archive" wizard.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/misc/ResourceAndContainerGroup.java
/**
     * Create an instance of the group to allow the user
     * to enter/select a container and specify a resource
     * name.
     *
     * @param parent composite widget to parent the group
     * @param client object interested in changes to the group's fields value
     * @param resourceFieldLabel label to use in front of the resource name field
     * @param resourceType one word, in lowercase, to describe the resource to the user (file, folder, project)
     * @param showClosedProjects whether or not to show closed projects
     * @param heightHint height hint for the container selection widget group
     */
    public ResourceAndContainerGroup(Composite parent, Listener client,
            String resourceFieldLabel, String resourceType,
            boolean showClosedProjects, int heightHint) {
        super();
        this.resourceType = resourceType;
        this.showClosedProjects = showClosedProjects;
        createContents(parent, resourceFieldLabel, heightHint);
        this.client = client;
    }
    /**
     * Returns a boolean indicating whether all controls in this group
     * contain valid values.
     *
     * @return boolean
     */
    public boolean areAllValuesValid() {
        return problemType == PROBLEM_NONE;
    }