It's too bad that these appmakers don't make a free app for testing. That's why i've waited for the release of mobilerss on the ipad. Which i'm familiar with on the iphone
The most important thing of that rss-app is that it syncs and download images on the background. You can continue reading in the meantime. This also means that it can sync/download when connected, and you can read it offline.
This is of course not mentioned in any app description, so I don't know if newsrack does that too.