THE GOLD STANDARD
Reeder is without doubt the best RSS reader for use with Google Reader. In fact, Reeder is simply the Gold Standard in apps of this genre. I've tried many premium readers, and as another reviewer commented, other apps either tend to be top-heavy on features or top-heavy on aesthetics. Until now, no app developer has managed to combine the two effectively. Reeder is fast, sleek, beautifully designed, unclutteted and does what you need well. Twitter integration coming in the next update (I'm a beta tester) works seamlessly as do the other share options. Even sharing an article by email creates a simple but elegant email with clickable headings. In short, it's just a beautful, simple app to use, and takes pride of place on my iPhone homescreen springboard.
I would argue that Tweetie 2 is the gold-standard of Twitter apps. By this virtue, Reeder is well on the way to being THE best reader app; the gold-standard of apps in it's class. I would like to see more features available, such as the ability to add feeds from within the app, and to be able to manage existing subscriptions, again within the app. But for now, I'm one happy Reeder!