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
.getUIInfoAdapter(getShell()));
				} catch (final ExecutionException e) {
					getContainer().getShell().getDisplay().syncExec(
							new Runnable() {
								public void run() {
									if (e.getCause() instanceof CoreException) {
										ErrorDialog
												.openError(
														getContainer()
																.getShell(), 
														
														IDEWorkbenchMessages.WizardNewFileCreationPage_errorTitle,
														null, 
														
														((CoreException) e
																.getCause())
																.getStatus());
									} else {
										IDEWorkbenchPlugin
												.log(
														getClass(),
														"createNewFile()", e.getCause()); 
										MessageDialog
												.openError(
														getContainer()
																.getShell(),
														IDEWorkbenchMessages.WizardNewFileCreationPage_internalErrorTitle,
														NLS
																.bind(
																		IDEWorkbenchMessages.WizardNewFileCreationPage_internalErrorMessage,