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/extensions/org/eclipse/ui/dialogs/WizardNewFileCreationPage.java
initializeDialogUnits(parent);
		
		Composite topLevel = new Composite(parent, SWT.NONE);
		topLevel.setLayout(new GridLayout());
		topLevel.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_FILL
				| GridData.HORIZONTAL_ALIGN_FILL));
		topLevel.setFont(parent.getFont());
		PlatformUI.getWorkbench().getHelpSystem().setHelp(topLevel,
				IIDEHelpContextIds.NEW_FILE_WIZARD_PAGE);
		
		resourceGroup = new ResourceAndContainerGroup(topLevel, this,
				getNewFileLabel(),
				IDEWorkbenchMessages.WizardNewFileCreationPage_file, false,
				SIZING_CONTAINER_GROUP_HEIGHT);
		resourceGroup.setAllowExistingResources(false);
		initialPopulateContainerNameField();
		createAdvancedControls(topLevel);
		if (initialFileName != null) {
			resourceGroup.setResource(initialFileName);
		}
		validatePage();
		
		setErrorMessage(null);
		setMessage(null);
		setControl(topLevel);
	}
	/**
	 * Creates a file resource given the file handle and contents.
	 * 
	 * @param fileHandle