Pretty awesome for the most part. A few minor-major gripes.

Rating: 8/10 (28 April 2018)

I will start by saying that I came in with absolutely NO expectations. I stayed away from any speculations, reviews, and/or trailers. That being said the film, for the most part, was pretty satisfying. There are rarely any dull moments, a lot of very good laughs, awesome action, and a great villain that isn't brain-dead and simply power-hungry. I actually give it a 7.5/10 but rounded up instead because I tend to be rather nitpicky.
To start with some of the pros:

The balance of character screen time was very good. I didn't feel like one character got too much while another got nothing. This was something I was worried about but it turned out very well.
The jokes were surprisingly very good. Many jokes didn't feel cringy, awkward, or forced. Most of them felt natural and fits the characters. Drax, specifically, was hilarious.
The villain was badass. He's not some random power-hungry monster. He's not some evil for the sake of being evil person. He's smart, powerful, and driven. He's calculative, has feelings, and can love.
Action was amazing. A lot of styles, art, and creativity. You like magic? check. Brute strength? check. Martial arts and weapons? Got it. Not to mention my favorite scene - when Thanos crushed AND threw the moon at them... yea, BADASS!
I also love how they made Thanos' minionrs or children extremely formidable themselves. They were all strong, quick, smart, and powerful. To be honest, they were stronger than most main villains in the majority of the other Marvel and DC movies. I appreciate that they didn't make them appear too "disposable" like most other minions or servants.

Now to get to some of the gripes I have that made the movie a bit "off" and less enjoyable:

Thanos' over-reliant on the Infinity Gauntlet. Yes, I saw what he did to Hulk at the very VERY beginning, but that's mainly it. The rest of the movie he mostly relied on the gauntlet to do anything. I started to feel like he was useless without the gauntlet towards the end. It would be nice to get a little more reminders that he doesn't NEED the gauntlet to still be extremely scary and formidable.
Some of the characters -COUGHstarlordCOUGH- acted extremely out of character. I was shaking my head and cringing at how awkward and immature he acted in one particular scene. Everybody has been losing a lot of friends and fights throughout the movie but he just threw a tantrum and pity party for himself.
The Hulk. He was a pansy the whole movie and refused to help anyone. Besides the very beginning, we actually don't get to see him fight at all. Not even once. Hulk was literally running with them in the trailer during the fight in Wakanda but in the movie he was in the Hulkbuster suit the whole time. False hype? Empty promises? A little misleading.
Near the end when Thanos wiped out half of the entire Universe, most of them died extremely peacefully. I felt like Spiderman had the most emotional weight that made me want to reach out and hold him to try and calm him as much as I can with however many seconds he has left. Most of the others simply grin or just stood there while they turned to ash. The deaths were tragic, the execution didn't feel quite right.

For the most part it was a good movie and I'm excited to see what they will do in the next episode.