You can get Pandora on your Apple TV. All you have to do is install Boxee on it. I just installed it a couple of weeks ago. It was super simple. Here are a couple of links to get you started:

http://boxee.tv
http://wiki.boxee.tv/AppleTV_Installation
http://boxee.blip.tv/#1418648

All you have to do is install the Boxee Launcher and you're good to go. Don't forget to add me as a friend on Boxee from the web application. I'm knilob on there too.