You're correct, the tooltip functionality that existed in the 1.x versions wasn't transferred into 2.x. Personally, I use the description element property to provide my users with any additional information about a form element. The description will be rendered in italic text below the element's label. Give it a try and let me know if that alternate solution works for you.
$form->addElement(new PFBC\Element\Textbox("My Textbox", "MyTextbox", array("description" => "This is a description of my form element.")));
- Andrew