Instead of just porting over the interface or at least the interface concept from the recently-released Facebook 3.0 for the iPhone, they've given us an Android-specific UI. Not that it's particularly Android-y; it's just different. The front page panels on the iPhone app have been replaced with a simple view of your feed, while the rest of the functions come by way of menu-accessible shortcuts, which require pressing a hard button.
Those other features include direct photo uploads, big fat "Like" buttons and, though I couldn't get this one working, a phonebook function that gives you instant access to 125 of you chosen friends' phone numbers. It's a slightly less intuitive approach than the iPhone app or even to a certain extent the web interface, but it's a far sight better than any of the third-party apps already in the market, many of which tried to pass themselves off as official, and some of which even had a nonzero (!) price. Facebook's official app, luckily, is free, and in the market now.
UPDATE: So, Phandroid's noticed a few odd things about this app: Despite the developer being listed in the Market as "Facebook," the developer's email address is a suspicious Facebook.Android@gmail.com, and the associated Facebook app-as in, for the website-says it was not developed by Google. Could we have an impostor here? That would explain the new design philosophy, and the lack of a few major features (messages, anyone?), but that the fact that it is a fairly polished app.
Source: Smokie's Writting Pad