I'd only seen Alien and Aliens before, but the trailers for this movie looked interesting and I was down to see a new horror movie. Good news though, you don't need to have seen all of the previous movies to get this one, it's a pretty straightforward sci-fi horror film, and a pretty good one at that.
For the good, the visual effects are top-notch. The practical effects in particular were effective. There were some really superb body horror moments, particularly near the end. The acting as well was great all around, although I did find it a bit difficult to understand some of the British actors' lines, but that could just be my ears. The music was also great; the score was very 70s sci-fi, which I appreciated.
The plot was decent, nothing special. The set-up for the action does what it needs to do, but I didn't get too invested in any of the characters, save for the main two, Rain and Andy. Once the horror starts, what was the plot disappears and it's all about survival, which honestly I appreciated because I'm not very invested in the franchise lore.
The horror was fun, but I was never truly scared (though that may be unfair, I rarely get spooked by movies). Most of the scares are jump scares, but there are some pretty good creepy moments and body horror parts, like I mentioned. The ending especially was effective horror-wise.
For the negatives, I would say there were a few classic horror movie contrivances, mostly the monsters walking really slow towards the main characters. There were also a couple iffy special effects, particularly with the WARNING: SPOILER - CGI Ian Holm inclusion. Speaking of, I wasn't a huge fan of the fan service moments, particularly that callback line near the end...
Overall it was fun, I recommend it if you're already an Alien fan, or just want to have a good time at the theaters.
Oh, and Andy is the best character, obviously.