Nightfall will be fun to seasoned players but I don't believe new players will have the same reaction.
All and all my experience with Nightfall is good and bad. I do like the 2 new professions, new skills, Egypt-Africa theme, the new endgame content(Via Mallyx), & Hero system(Sorta). And by "sorta" I mean I like the fact I can add a much more useful npc to my party to fill any need. But I don't like how it's cutting out alot of the players.
However what I don't like at about Nightfall is the early on Sunspear ranking stuff. Although anet did adress that issue by adding other ways to get past that but whatever you do to progress through the island your still limited by sunspear rank or level. I think that hinders the game from the beggining and can drive away some newer players who wont tolerate being forced how to play. Most may say Factions was the same way but at least you could bolt through that part in at least 2 days if you were fast and knew what to do.
But now that I'm done ranting, I did enjoy the game overall. Even though the beggining is a drag, once you get over that hurdle you may find you like the game.