My vote is for Portals/LFD. I don't like flying mounts or welfare epics either but it seems like the thing that really stopped making world of warcraft feel "worldly" when was blizzard allowed players to port all over the place without leaving their healthstone location (sw/orgi). Even in WOTLK pre LFD where welfare epics and flying mounts have been around since BC, playing WOTLK still felt "worldly" and it really felt like I was playing a massive mutliplayer rpg with tons of interaction with other players.
Cata in comparison seems to have lost all semblance of a "massive world" feeling.