Inserting a contact form into a page works in 3.9, but also inserts the following error text above the form.
Warning: strpos() expects parameter 1 to be string, array given in F:\xampp\htdocs\wptest\wp-includes\shortcodes.php on line 193
This was on a fresh install of Wordpress 3.8, which was then upgraded to 3.9 with the default theme and only Jetpack installed, the same behaviour is not found on 3.8.