Bucky was not very fond of Tony and the way he made fun of Steve. He didn't tease Bucky nearly as much as he teased Steve. However, Tony eventually grew on him. As Tony slowly (very slowly) ran out of new nicknames, Bucky became closer to him. In a friendly way, of course. Bucky still had feelings for Steve, obviously. Bucky knew Steve liked him, too.
Tony, on the other hand, was constantly making fun of Steve and Bucky's love. He thought the fact that they tried to hide it was even funnier, so he always made sure they knew that Tony wasn't blind.
Clint, who even though was named 'Hawkeye', usually had no clue about anything. He was literally blind as a bat to anyone's emotion except Natasha's; and even he could see the romantic tension Bucky and Steve. Natasha thought it was adorable. Them, always blushing and grinning at each other was so cute. She liked how they were both so shy and secretive about their relationship. Even if it didn't quite "exist" yet.
Bruce didn't really care if Steve and Bucky were together. However, Bruce felt he had a connection with Bucky that even Steve didn't have with him. Both had "another guy". They both couldn't really make him go away, and Bucky was the complete opposite of Winter, just as Bruce was to Hulk. He liked having Bucky as a friend.
Sam teased Steve about it, even though he knew Bucky would kick his ass any day of the week. Otherwise, it made him think about his old partner. He missed him, but he never had romantic feelings toward him.
Nick Fury didn't give a flying fuck.
Neither did Agent Hill.
Steve loved Bucky with so much passion that it hurt to look at him. His heart was heavy with his presence. Even though some of "the new Bucky" wasn't familiar to him, he kept faith in his friend. In fact, Steve might adore the new Bucky more than the old one. Things were simpler back then, but things were better now. Steve had taken the new Bucky and stopped looking back to the old one. The new Bucky was absolutely perfect.