I have not really used LinkedIn. In fact, I created an account today, so I could test out their new iPhone app. I saw the UI from the iTunes App Store screenshots and I was intrigued by how simple and easy to use the User Interface looked. Of course, as you all know, I think the most important aspect of an iPhone app is the User Interface, then features.
After using the app for about 15 minutes I was very pleased with how easy the app was to use, considering the actual LinkedIn website is very clunky (though the recent redesign is much more aesthetically pleasing), and for someone like me who went to LinkedIn for the first time, I found it very hard to use and to find/edit my profile.