The most important part about Facebook's new iOS apps that they unveiled yesterday? For starters, the app actually works and I had given up using Facebook for iPhone (which failed 90+% of the time. But other than the obvious... the below screenshot is the most impactful aspect of the new mobile suite. It gives users the ability to access and use applications directly from within Facebook Mobile. That is convenient for users and represents future opportunities for deeper developer & Facebook integrations (think 'canvas apps' within the Facebook apps). And to developers / publishers, this is remarkably valuable real estate that drives engagement and mobile usage / downloading: for instance, when I clicked on Instagram, it took me directly to iTunes to download the application (I have it on iPhone but not iPad).
Also interesting: Facebook clusters their own products within "Apps" - and it is done alphabetically (I would think they would mark their products atop the list): Events, Messages, Photos, etc.