I really liked it. The ending had me nerdgasming, the new line-up seems so promising
I do wonder how long it will last, as I doubt Tony, Thor and Hulk will stay off the team for long. I was surprised Hawkeye didn't remain on the team as the movie really focused on why he's an integral part of Avengers, but I can't say I'll miss Renner. I enjoyed how they established his family and all, but at this point the comic version seems so much more interesting. The biggest downsize of giving him a family is that it makes it harder to adapt Fraction's run to a Netflix series (I'd have LOVED that so much).
The Hulk/Natasha pairing seemed incredibly odd at first, but it actually grew on me. I think it ended up working in the context of the movie and it's definitely not the weirdest Avengers pairing, but I wouldn't like to be such a big focus in the future. Natasha should stand on her own for a while.
Another thought I had while watching it is that this could have been a great way to introduce Spider-Woman. I know there were already a lot of characters, but with the plot about Scarlet Witch and Quicksilver gaining their powers due to experiments by Hydra, it would make sense to at least hint at the existence of someone with a similar backstory. The ending with the introduction of the "New Avengers" made me want this even more and I still hope Jessica is introduced soon, maybe even in Agents of S.H.I.E.L.D.