I don't know a single person who has Facebook and doesn't check it on their phone. I also don't know a single person who doesn't hate how ridiculously slow the official Facebook app is. Fortunately, Facebook has APIs that allow third-party applications to do everything that you would normally use the official app to do - and it many cases, they do it better. A good example of "doing it better" is Friendcaster fro Facebook, which just so happened to receive an pretty massive update to version 5 today.
Version 5 brings many new features to the app, but the most notable is the all-new interface (which looks absolutely fantastic).