The art team has done a fantastic job. There are a host of new effects in the new zones. The trees in Greater Faydark are absolutely ginormous, and the terrain below the platforms of Kelethin explain why one would want platforms in the first place.
One of the visual treats to look for (at "Balanced" performance) is flying things. In GFay, its birds. In Loping Plains, home to vampires and Mistmoore Castle, its bats. These are non-targetable animations. I first saw these in Loping Plains, flocks of bats flying over my head into the horizon. They flitter ands swirl in a flock, like something out of a Dracula movie.
The same technology gives us leaves that float gently to earth in our field of view in Greater Faydark. And there are probably more examples of this elsewhere in the game.
In Steamfont Mountains, there are geysers. They erupt periodically, and leave a fine spray, which sometimes produces a rainbow. The eruptions can be ridden by a player character and seem to do no damage, though a high enough fall might be a problem for someone without safe fall.
And then there are capes. The animation of cloth that dangles freely is no small feat, and requires intensive computation. Which is why they cheat a bit and don't calculate collisions with every single body part. As a result, you can sometimes see legs or elbows sticking through a cape if you look closely. Still, they look good.
The lighting effects have changed too. Often characters or monsters will seem to glow in the light, due to a spell effect or just the lighting conditions. This doesn't seem to be unique to the new zones either. Sometimes this seems a bit much, though it certainly seems appropriate for the Fae wings.
There's probably more visual richness to be seen, but those are the high points I noticed during my whirlwind tour. Post a comment if you see something else noteworthy.