I picked this up at a Target not long ago and I was pleasantly surprised. I'd never heard of the game before, but I checked out a GameSpot review, which compared it favorably to games like Freelancer. I loved Freelancer, so I bought Darkstar One immediately. I am very glad I did.
It's different than most space sims in that you don't change ships. You're flying the same ship through the entire game, although you can upgrade it. How you upgrade your ship determines how it flies and fights, which makes the game seem almost RPG-ish.
My main complaint is that the side missions get very repetitive, as can be expected. Escort this guy, shoot this guy, gather this material, etc. However, the storyline is very engrossing. It takes you throughout every region of the game's universe, slowly introducing you to the different races and giving you interesting missions. I haven't yet played to the end, so I have no comments on how the story ends, though I suppose it'd be bad form to reveal too much in a review.
Graphically, the game is very good looking. I'd recommend a pretty decent machine if you want to crank the settings up all the way. I haven't run into any technical issues, but keep in mind that I'm not working with GOG's version.
Another minor complaint is the voice acting. It's decent, but a bit amateurish at times, especially with some of the alien races. But I've certainly heard worse voice acting, so it's not too distracting in this case.
Overall, this is an excellent game for people who enjoy space sims. I'd recommend it to anyone, really.