I love the character models. Not just artistically pleasing, but graphically pleasing. Such animated and expressive faces!
I'm enjoying the music- RIFT is a game I stopped playing, and I realized that lack of a soundtrack was a big reason for my disinterest in the world.
I feel like there is something for me to learn in every battle- not instantly go, "oh this is my most efficient attack, time to stand and spam, collect loot"
I'm grouping with my husband and some friends on most sessions, and everything is very group friendly. I completely stopped playing Champions Online because group questing was so absolutely broken.
And this is the big one- the camera and controls are remarkably smooth and intuitive despite being completely different than any MMO I've played before. This was an issue in SWTOR, I felt like I always had to jerk the camera around and it was never where I really wanted it to be. But with TERA... I don't need to be a spell clicker anymore :p Its that easy!