Plugin no longer works correctly when used with the wysiwyg plugin
Since the timing and estimation plugin was updated to put the 'Add hours to ticket' field just below the comment field (and above the 'Modify Ticket' section), the field becomes invisible when the wysiwyg comment editor is selected.
Install trac 0.12, with timing and estimation tools plugin for 0.12 (I am using an export from svn rev 9643), and wysiwyg plugin for 0.12 (I am using an export from svn rev 9251). Enable both plugins in a project. Now choose the "wysiwyg" radio button just below the "Add a comment" header. When selecting "wysiwyg", you should see the "Add hours to ticket" field and stopwatch disappear. Selecting "textarea" should make those fields re-appear.