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
nameGroup.setLayout(layout);
        nameGroup.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL
                | GridData.GRAB_HORIZONTAL));
        nameGroup.setFont(font);
        Label label = new Label(nameGroup, SWT.NONE);
        label.setText(resourceLabelString);
        label.setFont(font);
        
        resourceNameField = new Text(nameGroup, SWT.BORDER);
        resourceNameField.addListener(SWT.Modify, this);
        GridData data = new GridData(GridData.HORIZONTAL_ALIGN_FILL
                | GridData.GRAB_HORIZONTAL);
        data.widthHint = SIZING_TEXT_FIELD_WIDTH;
        resourceNameField.setLayoutData(data);
        resourceNameField.setFont(font);
        resourceNameField.setBackground(
        		FieldAssistColors.getRequiredFieldBackgroundColor(resourceNameField));
        validateControls();
    }
    /**
     * Returns the path of the currently selected container
     * or null if no container has been selected. Note that
     * the container may not exist yet if the user entered
     * a new container name in the field.
     * @return The path of the container, or <code>null</code>
     */
    public IPath getContainerFullPath() {
        return containerGroup.getContainerFullPath();
    }
    /**