Tera is exceptional because of its action combat system, which puts pretty much every other MMOs to shame.
It also has artistically pleasing and colorful visuals.
Otherwise, its quite standard, and the quests while leveling are incredibly standard fetch and kill quests, ALL the time.
Yet I liked it a lot, purely because its action combat system is really fun. I'm personally hoping I can get a team of 5 to go through this game and its dungeons -> the dungeons being the most fun part of the game, since they are somewhat skill based and just overall fun to do.
Thats the thing, the game is much more a dungeon-game than a MMO game. The whole MMO aspect is just not very good, but it has some great stuff in it.