Well after playing Nightfall I thought I would give my point on it. To start, Nightfall is very well put together. The story line seems like it will be very indepth. Nightfall IMO blows Factions right out of the water, and seems like overall it may be just as much or bigger in storyline than Prophcies was.
There are some new spells that are very nice and I'm sure will change the way pvp and gvg is played. For example, Elementalist have this earth spell that is "armor" that cuts damage by so much depending on your earth skill level. If it's high enough it can basically cut all damage down to nothing.
The new hero system is nice. Along the way you get these hero's that you add to your party that go along with the quests or missions that you are doing. You can completly customize your hero's anyway you want. For example, the first hero you get to use is Koss, who is a warrior. Hero's get all of the spells you have unlocked for that job, so Koss has all the warrior skills I have unlocked. Also, hero's can have a secondary job. So I made Koss a warrior/monk, which means he also got all the spells that I have unlocked for the monk. You can equip your hero's with new weapon's and armor, dye it colors, and redo their attritubte points to match the skills they are using.
So far I only got 3 hero's that joined in on how far I got. I'm assuming that as the story goes on you will have alot of different hero's to choose from. As far as I know you can only have 3 hero's in your party at a time. The hero's do level up just like you do.
The new UI is better in my opinion. When out in the world on your compass you have little control buttons that you can use to send your henchmen and heros to move to different places on the map. On your mini-map and compass now also displays the "collectors" that are out on the field.
Overall the whole world map seems bigger, and there seems to be tons of quests to get while you are outside in the world. I would say in my opinion that Guild Wars: Nightfall will be the best yet so far. For those that are thinking about getting into Guild Wars, this should be the one you get.
Well that's my afterthought about the game. 1 month to go till release and I can't wait.