Having played it a bit, I can confirm. It's hands down the most beautiful map in GW2 I've ever seen. The music is great, and it pays a lot of homage to the original Nightfall campaign.
Mounts were definitely the highlight of the experience. It's kinda hard to describe, but they feel really organic when they move. It's not like a player character, there's a lot of momentum to riding a mount, and it just feels really good.
The new expansion seems to address most all the complaints from Heart of Thorns. I spent hours just wandering around the City of Amnoon, listening to the different NPC dialogue. Unlike Heart of Thorns, it genuinely felt like one of the original maps, but next-gen and polished.
There's supposed to be another beta this weekend. We should organize a MoTK squad explore it together with a bunch of Beta characters named after Touhous!
Add me: Kain Francois.4328
edit: An album of the new landscape. Yes it's beautiful.
http://imgur.com/a/MAcJ2