You can just download the iPhone app to the iPad; HOWEVER it won't be maximized for the iPad resolultion and must be expaneded in order to fill any substancial portion of the screen.
The dedicated iPad app is a totally diffeent animal altogeather and requires another license to be purchased. It offers a much better resolution and interface specifically intended to maximize the iPads screen. Well worth the additional 30 bucks.
You must have a solo or HD pro for the iPad app to work however!