It's worth it if the class you play doesn't get nerfed. I played Destruction Warlock for ever and i was full heroic thunderforged. The new patch came out and fucked my class so i quit. Haha
Yeah it's fun if you like building character and constantly having better stuff to obtain. It may seem slow at first but once you hit level 15 and start dungeons or PvP at level 10 things start to get less boring.