First off, let me say that I thoroughly enjoyed this film and will probably see it again in the theater to try and catch more Easter eggs. I highly recommend seeing it, but don't bother with 3D.
Among my favorite bits in the film:
• Bucky, Cap, & Falcon - lots of good moments between these guys.
• Ant-Man - Paul Rudd delivers again. He has some very memorable moments, but my favorite is still when he meets Cap for the first time.
• T'challa is outstanding. Not sure where they will go story-wise for his solo movie, but he has a great story arc.
• Spidey - They did a good job casting Tom Holland. They definitely got to the heart of Peter Parker/Spider-Man in a way the last two movies didn't. I'm not too keen on their casting for Aunt May, but I'm willing to wait on his solo film before I form an opinion.
The Scarlet Witch & Vision arcs were good, but not stellar (hers was better than his), but they almost need another film to really flesh those characters out.
The writing and pacing were excellent. The Russo brothers did an amazing job getting that many characters on screen without things becoming horribly muddled.
Some of the the fight scenes (especially the first) have a bit of that thing where the camera is whipping around to make the action seem really frenetic. Fortunately, the later fights are longer shots and better composed.