i am sure many would have realized how different facebook looks by now. not all changes are for the better but think this is one of the good ones.
facebook now have a brand new layout. doesn't look that much different but certainly looks cleaner and more organized. not as lightweight as the facebook lite but not as cluttered as the previous version. all the menu at every corner of the page (all top, bottom, left and right) have been something i didnt like in the previous version. now there is one menu less and i welcome that change.. little as it may be.
what changed? generally they created a better dashboard and put applications and notifications there. and they added sort of a counter function to it. pretty neat.
read details about the update at the facebook Developers Blog