Nothing too special or orignal but the full game promises to be a solid example of the genre.
You face a seemingly hopeless apocalyiptic wasteland (sound familiar); you just barely eke out existence with death only a blow away (hmm, even more familiar). Absolutely amazing given that only two people developed this game; judged otherwise though (by professional company standards), the story, progression, plot, and last boss were sad disapointments.
Its hard, fun, and old-school; there's secret levels, pain in the posterior bosses, and arcade levels that you have to play perfectly and then have a little luck. On top of all that it even gives Microsoft some well deserved bashing and goes deep with its story; overall, the only thing I would improve would be fixing some of its glitches and making the fourth episode feel less automatic (you've fully upgraded your ship at this point). (P.S. One of its minigames is the unofficial mini-game of the Last Supper.)