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
.getRoot().getFile(resourcePath).exists())) {
            problemType = PROBLEM_RESOURCE_EXIST;
            problemMessage = IDEWorkbenchMessages.ResourceGroup_nameExists;
            return false;
        }
        return true;
    }
    /**
     * Returns a <code>boolean</code> indicating whether the resource name rep-
     * resents a valid resource name in the workbench.  An error message is stored
     * for future reference if the name does not represent a valid resource name.
     *
     * @return <code>boolean</code> indicating validity of the resource name
     */
    protected boolean validateResourceName() {
        String resourceName = resourceNameField.getText();
        if (resourceName.length() == 0) {
            problemType = PROBLEM_RESOURCE_EMPTY;
            problemMessage = NLS.bind(IDEWorkbenchMessages.ResourceGroup_emptyName, resourceType);
            return false;
        }
        if (!Path.ROOT.isValidPath(resourceName)) {
            problemType = PROBLEM_NAME_INVALID;
            problemMessage = NLS.bind(IDEWorkbenchMessages.ResourceGroup_invalidFilename, resourceName);
            return false;
        }
        return true;
    }
}