There is no extended cut, it's been confirmed.
Thinking about this movie, I wonder what impact Infinity Wars will have on perception of it, will this movie end up just a stepping stone from Avengers to Infinity Wars and once you have that final piece it'll seem better and only looks weaker now seen just as a sequel story to existing films, or will it always feel the same to people.
I was thinking about the comments about how characters were all similar and I was thinking about Barton's extra story here and why people don't like it. I think part of it may be because they're trying to give Barton story without giving him his own movie, but, unlike Thor or Captain America, Iron Man or Hulk, where their back stories set up their motivations and explain how they are the way they are today, Barton's family life and how he is on the team have no connection outside of a forced speech to Scarlett Witch, he doesn't act fatherly towards the team, he doesn't act like he's fighting to save the world for his family, he just acts like a SHIELD employee. I feel like if his backstory enhanced our understanding of what he's done to date and through Ultron, it would be more accepted, I think people don't like it because it doesn't really add anything to him.