I think they did a good job introducing t'challa/black panther. we really got to know him as an individual rather than a member of team iron man, which he actually wasn't. he had his own personal mission of vengeance and fought with stark only to get his claws out (literally) on bucky. it has me looking forward for his movie.
i was hoping to see more of black widow, but they showed her struggles well in the time she got. on one hand, she has a great friendship and bond with cap, especially after the winter soldier, but on the other hand, she has to be on the government's good side to redeem herself. she fought with stark, but her heart was with cap. she was a worthy double agent.
i think i was supposed to be annoyed that spiderman was getting rebooted again, but even before seeing the movie i was adamant it was going to be a good move and after seeing it, my opinion didn't change. it was great that he was played by a younger guy rather than a 30 year old pretending to be a high school student, and his connection with stark makes way for a different twist to his story than what we see in the other spiderman films.
Sharon carter only got a few minutes screen time and she was only there to make out with cap in a forced romance, but should she appear in future films, i can imagine her character being more developed.