I’ve seen it last night. Short version - it’s good. It’s not excellent, but it’s not bad, it’s just “good”.
Long version -
Good things :

pacing is done correctly, the movie is fast when it needs to be fast and it’s slow when it needs to be slow.
action - every action scene in the movie (at there’s a lot of them) is GREAT.
effects - most of the time I had no clue what is real and what’s CG, which is a GOOD thing and a huge improvement to Age of Ultron
the whole movie is entertaining
nice Star Wars homage / rip-off

Bad things :

new characters are not developed properly, basically they’re not developed at all. I think they made a huge mistake that they didn’t do solo movies for Spiderman and Black Panther before this movie.
what the hell are exactly the powers of Scarlett Witch and Vision? Every single time they did something I was just staring at the screen confused. I know her powers were introduced with “weird” in Ultron but did Vision have these powers? Explain, movie !
Spiderman. Not sure how anybody can like him. I am a huge fan of the character and the Raimi movies, and I hated Spiderman in this movie. He was almost as annoying as Jar Jar Binks. You are watching something which should be an emotional battle between close friends and the tone gets suddenly interrupted by Spiderman acting nervous, clumsy, or throwing some funny one liners. For the first (and maybe second) time it was quite funny, but as he kept on continuing I was seriously like “Shut the f up!”
Captain America was portrait as a complete asshole in this movie. I liked him in the previous movies, Chris Evans has portrayed the most charismatic superhero since Chris Reeves’s Superman, but in this movie he basically abandons all his friends, and his government to basically help a serial killer who used to be his friend decades ago. The real Captain America as developed in the previous movies would try to arrest him and trust the system. The new captain just fights his friends without any good reason. Even in the trailer Tony says with an confused voice “So was I …” when Cap says “He’s my friend”.
Deaths - not wanting to spoil anything, so let’s just say I’m not satisfied with the deaths in this movie
the villain. Oh yes, there’s a villain in this movie. Why? I don’t know. He’s the most pointless villain I have ever seen in a movie (ANY movie, not just MCU movies), this is the first time when I think that cutting out the villain out of the movie would actually improve the movie.

Overall a good movie, but not the masterpiece most people call it.