Facebook for iPhone doubles as a massive phonebook

There's been a lot of buzz over the iPhone optimized version of Facebook in the past couple of days, and with good reason--it rocks. It does nearly everything the full version of Facebook can do, sans apps from the Facebook apps platform, which I assume are on their way later this year. Everything is rolled up into a tight little package using a simplistic set of two rows of tabs to cover core navigation, and a sliding interface that mimics the iPhone's signature UI. To get there, just point your iPhone (or browser) to http://iPhone.facebook.com.
If your friend's listed their phone number, you'll be able to call them with the touch of a button.
Like the full version of Facebook, the iPhone iteration centers around your profile, friends, messages, and the home tab, which contains the Facebook news feed, along with any upcoming events and notifications. You can browse profiles and check out your friend's links (which open up in new Safari windows). The real killer app though is the call option, which will pop up assuming your friend has made their phone number available. This works with e-mail addresses too, but the phone numbers basically turn Facebook into one big mobile phonebook for your friends.