NetNewsWire was part of the iPhone app store launch, and will be part of the iPad App Store launch as well. The iPad version is redesigned for the bigger screen real estate to give you almost the full article at one glance. NetNewsWire syncs with google reader so if you read an item on your iPad you don't have to go through the same article on your mac or iPhone, or Windows with FeedDemon. You can save articles for later using built in Instapaper function, or even email or post to twitter.
NetNewsWire for the mac is a free download that comes with ads, and to buy the full version it costs $14.95. The iPhone has a free version, and a $4.99 premium version that removes the ads. For the iPad Newsgator has decided to just offer a premium ad free version for $9.99 in the middle of the mac and iPhone versions.
The iPad app looks very similar to the PC version in terms of interface with your feeds on the left, and the full screen article in the main window. Plus it has the touch screen functionality of the iPhone version, so is $9.99 is something you're willing to pay for an RSS reader? The price and screenshots are subject to change.