The Avengers finding Thanos (& killing him!) that early in the film surprised me. I liked the scenes Captain Marvel was in but felt she should have had more screen time. I enjoyed Professor Hulk, but we needed to see that change happening; not have it explained to us in the past tense. I enjoyed seeing the epilogue from the Battle of New York where Robert Redford, Sitwell & Brumlo show up. Loki's reaction when the Tesseract just slides to his feet was priceless! I wish we could have seen more of the Vision; always felt him underutilized in the films. Would rather have seen Betty return from Incredible Hulk than Jane Foster, but I guess that would have made Bruce's reaction to Widow's death more complicated. Noticed we haven't seen Bruce & Secretary Ross speak since Hulk's return to Earth; would like to have seen that.
When Black Panther & family walked on to the battlefield, everyone got silent; but then when EVERYONE else started to return also, the audience started cheering & clapping! Obviously the battle that followed was amazing, but will require viewing again at home for closer inspection to catch everyone because I found it a little dark to tell clearly who was fighting who. When Steve went back at the end to return the stones, wish we could have seen him meeting the Red Skull! Also wish Tony had run into Bucky on the battlefield; perhaps when Tony snapped his fingers, then Bucky would have vanished also! I know in recent comics, The Falcon becomes the new Captain America, but I just don't see him carrying a film solo. Tony's death (obviously foreshadowed at the end of the Battle of NY) was not that surprising to me because one of my favorite comics from the 70s was What If#3 (What if the Avengers had never been) ended the same way and still is my favorite ending to a comic.
BTW, during Tony's funeral, back by the cabin is a tall boy standing alone; at the time I could not place his identity. Turns out he is the kid from Iron Man 3! So the next Guardians film looks like will also star Thor; interesting....