So I'll throw my two-cents into the ring.
The story is very simple but it works.
Following an outbreak on the main ship the rest of the crew escape for someone to be infected and we don't know who. Shortly thereafter the Alien does make its appearance and with nowhere to go the crew is lost and make one final plea to not to even open the ship up. It's not even worth the rescue.
All things considered that's pretty dark of an Alien story where there is absolutely no hope. We have no idea who is playing host to the creature and we see that even the larval form is a threat that can get away pretty easily and start this whole mess over quickly.
The FX aren't great
We hardly see the Alien, and we in this case don't need to see it all. What little we do is fine for the short because I can't imagine they have the largest budget in the world. The issue at hand for me is that the compositing of the actors to the CGI elements doesn't really work as well as they should. It's fine for what it is but something a little more seamless would've worked better.
The acting is alright but not incredible.
Some of the line reads aren't great like when the lady locks herself behind the door, but otherwise these are actors who are trying to use what they have with the camera angles they got. It doesn't help we don't really have a "lead" character so to speak so we have wider shots with actors knowing that they have to make it work from all angles and playing up that an Alien is in the room when it really is a low end puppet.
Otherwise as nervous as I was about these shorts, Containment gets a B+.
It has its share of issues but most of that is budgetary and it does well with what its got. I give it props for doing what it did in the short amount of time it had and it's fairly entertaining. I don't know if I would seek it out if this was specifically on a DVD or Blu-ray, but I feel like this is potential for a full film where this "infection" jumps ship to ship and risks jumping to an active population center. I'd be willing to see a followup to this.