Not a fan, but I think they're a nice addition to the game.
I like doing some exploration, so the hearts, skill challenges, and vistas all seem like welcomed ways to get people to explore content, kill a wider variety of mobs, and generally spread out through the world more.
When I found my first regular vista I thought, "Heh...neat little cut scene! Nice job! Could lead to some interesting fraps videos depending on what's going on in the background." Then I went looking for my second vista and...well, my heart dropped a little bit. Towards the ground. Because I fell off a jumping puzzle.
And then I cursed.
ME NO LIKEE JUMPEE PUZZLE!!!!
I'm torn because I'm a bit of a zone and quest completionist, and there's free treasure to be had for doing so...kinda hard to resist the call of the gratuitous treasure box! But to do it, I have to do somethings that I really don't like doing at all.
*insert internal conflict here*
GAH! It feels like I'm being asked to put down my own dog because she acquired rabies. Some people love this kind of stuff and that's why I think it's a great addition. It's something different to most MMO's..."just a bit of a break from the norm." And I know that, in time, I'll do every single one of them. The completionist in me and the call of the treasure are sure to win out.
I just. Won't. Like. It.