New skills, new places to explore, friends, new partying methods, and talking to guildies/friends xDD
And PvP is actually a really big factor of my leveling incentive too 8D I love to be at the PvP grounds, and I get pretty annoyed when somebody blocks the way and just hits everyone that tries to get across, so I either ignore or leave to level xD
I also level for more money and quests o: Repeat quests actually give me a purpose, because if I'm not above 50%, I don't like grinding very much ^^;