no problem. yes, i have. when i connect my iphone it says there are no rented movies avialable to synch. but on itunes there is a rented movie under the rent icon.
By reading your posts, they seem missing or incomplete on this end. Maybe I'm not loading everything. Anyways. It's more of a manual process from what I've seen on mine. Go into itunes with iPhone connected. Click on iPhone from the device list. Now go to the content, and you will see where you can specify which rental to move to the iPhone.
After that, I can't help as I haven't done it yet. I'm waiting for my Apple TV software update before I even think about doing rentals.