I just got Nightfall as my brother wanted to try it.
It has the same feeling that I felt when I played the first one for the first time. So that is a very good thing for it. Makes me realize how much Factions was a letdown for me. Eventually I will go back through Factions with a toon and complete everything though.
As for Nightfall, having a Hero is very nice. They are much more commandable then the henchmen. Each also can have a skill set, just like yours. Also you can click on their skills just like yours to force them to use a skill. Great if you get them some healing skills and they are ignoring them. Also you can equip weapons and offhands/shields on them. Which is very nice. Their armor auto scales so you don't need to worry about that.
Overall I think Nightfall really brings some life back to a game I stopped playing.