1 - Level layout. Less invisible wall and more free terrain, gives the sense that there are less restrictions. Factions was a step in the right direction, but NF takes it further with giant open planes as far as the eye can see. Very nice.
2 - Setting. Asian and European fantasy has been done to death. I can't belive what a breath of fresh air this north african setting is. It's so refreshing. I havent said that about an RPG for almost a decade! The new enemies are great too - The termites and Corsairs are fun to fight. I enjoy the structures and armor aswell.
3 - Much easier to get into. GWP and GWF where a mess to get into. How many people did ArenaNet lose on that account? Now it's easy - Even the beginner quests give you the materials needed to craft new armor. This means that pretty much right of the bat you are getting new stuff for your character which is a real motivation quicker. Many people dislike the hole salavage thing and don't understand why they just can't loot the armor of fallen corpses. They don't understand or like why it needed to go out of your way to trade and find and grind certain things to get a certain piece of armor. This makes it much easier for them. At least here in the beginning.
4 - Better and more consistent loot. In 15 minutes in planes of Jahiri(spelling?) I got silver dye, istani key, tons of weapons, gold from almost all foes and so on - This is great. This is awesome. I understand that I am also biased because of the novelty of seeing all these new items, but seriously - More and more and more varied and consistent loot makes the game so much more fun. I hope Nightfall will be like this throughout the entire game.
5 - Quests are much better than in the previous two chapters. Suddenly I think im reading the quests again. Some of the dialouge is actually pretty witty and funny. I like the dude who is self proclaimed the best chef in the world, or the worried mother which son decides he want to be a Corsair because they speak funny. But quests are also easier, and simple - Straight to get into and out of. Exactly what you want them to be. The missions are there to tell the story and get you pulled in - Quests are the fast little excuses, but unlike the other two chapters quests which felt really really repetitive and lame, had horrible dialouge and the same repeated NPC throughout entire sections of the games, have been replaced by much more amusing quests, while fast and easy, makes you feel that you are accomplishing something. Making some easy money - Quickly and instantly getting you to new places - New NPCs - More easy to get loot.
I also like how the game tries to tie into with the two chapters - The little short story with the black Moa bird was a nice touch I think.
6 - Voice Acting has been improved dramaticly(Koss FTW:-D ). It means so much... to the hole game I think.
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I think all these 5 reasons will help get skepticals into the game, but even myself as a veteran am enjoying the PvE side of things more than I have in the previous two chapters. The level progression is faster than GWP but slower than GWF. It seems just right.
I guess though... If I had to say something negative it would probably be about the new amount of customization features. I really think both the Deverish and Paragon could use alot more features, but also more haistyles for the other ones. I don't know why they removed the afro hair and Mr. T style hair for the warrior for example. Maybe it's time to add extra customization features like beard, pircings and eye color? Maybe in chapter 4, or later.
I mean it's not perfect or anything. But I feel that NF is such a big step forward from the other two games. If the rest of the game holds up to this quality, then im sold.

In fact I like how they are doing Nightfall so much, that I wish they would go back to GWP and GWF and try to introduce some of these new subtle changes. I can understand them if Heroes will never make it to does chapters, though it would be cool, but other parts would be great.
Thanks for a great event, ArenaNet. Probably the most fun time I have had with Guild Wars since the WPE in October 2004, before the game was released. It's been as fun as the first moment I stepped into Lions Arch for the first time, almost two years ago now.