You can not like anybody's comments. Big deal for some, not for others. Otherwise so far that might be it... I think at one time you couldn't accept Facebook invites... not sure if that is still true.
There is one thing that bothers the **** out of me and that includes the app and the baked in stuff. My feeds on Windows Phone are FULL of stupid game notifications... Like Billy Bob's unlocked X from LameGame. This is on the recent feed option.
The kicker is that on the web version, or on the iOS or Android client using the same feed, all those stupid annoying things never, ever show up. I've hidden those things and they stay hidden on every other version but Windows Phone. That's why I grab my LamePad 2 or go to my Windows 7 desktop when I want to do some hardcore Facebooking.