Depends on what you are looking for...

Rating: 6/10 (10 June 2017)

I see a lot of 1 or 2 star reviews, which makes me wonder what rating scale is used. Even just for the visual experience the movie deserves at least a 5.
Now, with that out of the way, I have to say that I liked it, but at the same time understand that this movie doesn't win over the crowd expecting an Alien reboot. To be honest, I really wonder how you would expect a reboot of the original. How many variations of being trapped with an alien in a spaceship can you imagine? The AvP series prove that there is quite an audience for just making movies that feature xenomorphs in battle. I guess everybody understands that someone like Ridley Scott would try to make something better and bigger.
Prometheus in part succeeded in giving the franchise a backstory to further explore, but it also contained the unsympathetic and famously stupid characters, which made it a mixed experience for me. Unfortunately, Alien Covenant is another mixed experience. No cringeworthy character reactions towards alien life forms, but the movie fails to set up it's characters in time before they are killed off. The only two human characters we care about are the two that survive. That's not coincidence, that's bad screenplay. This makes the whole xenomorph elements a bit boring, because I don't care about it's victims at all.
The movie really is about David and Walter in their own little interpretation of Milton's Paradise Lost. David is Lucifer, looking down on both humans and engineers as inferior beings, which gives him the right to destroy them and Walter is Michael, protector of mankind. This is the strong part of the movie and Fassbender really steals the show on a level that surpasses Prometheus.
I guess if you are not at all bothered with creation on a philosophical or religious level, this movie raises an eyebrow. If you just came to see it for the xenomorphs it's even worse. I was quite happy, though. I saw the best Lucifer performance in a while and the movie finishes on what can only be described as the darkest cliffhanger in years.
Now, I feel like I have defended it enough, so here's some issues:

if the original form of the xenomorph is flying black liquid that turns it's host into a xenomorph, then the egg and facehugger seem highly inefficient.

What did David experiment on? He was on a planet without any animal life...

It's unlikely this was the engineer's home planet. Wouldn't they check out the colony that was just sterilized with their own bioweapon?

Let's assume Earth like planets like this one exist, still not a good idea to walk around without a suit and mask on. don't know what germs fly around...