Facebook Messenger for iPhone has gone 4.0 and includes some UI improvements as well as support for the iPhone 5's larger display. The conversation view has a new design and now you can swipe left anywhere in the app to quickly see a list of who's available to send message. At the top of this list you can also mark the friends you message most as favorites. The speed and reliability of Facebook Messenger has also been noticeably improved.
I never thought the day would come where I started liking Facebook apps (no pun intended), but Facebook has been doing a great job with their recent updates. This update to Facebook Messenger is no exception.