(Yeah I did this for the achievement, time to see if I got coal, coupon or game...)
Surprisingly good for such a cheap game. The graphics can be awesome - if you're into Mars geography, you'll wet yourself. Gameplay is fine, it's a general arcade shooter - no targeting, just shoot in front of you. Friendly AI actually do their jobs, getting kills, getting killed, and engaging enemies you're not engaging.
Plot, music and voiceovers should be taken less seriously. The finale isn't epic, but it's still a fun game for a couple of days.
Space bits might reminder you of a stripped-down Freelancer (but it's a shooter, not sandbox), graphics might remind you of one of the X games, and the on-planet bits will definitely remind you of Rogue Squadron.
P.S. Play on easy.