Let me first point out that most of the highly negative reviews are from people that are either REALLY upset that their favorites shows were canceled, only want some super techie expensive POS, or don't have the mental capacity to understand what kind of depth and hard work went into this show.
That being said, I am a very picky viewer. Half the shows on network TV claiming to be Sci Fi are watered down and barely beyond their "grounded" approach to the genre. Defiance is first and foremost, Science Fiction.
I admit, the show started out really rocky. The pilot was confusing to a degree, and the limited budget was apparent. But unlike a lot of attention inept who've posted reviews after giving the show 40 minutes of their time, I stuck it through. Two seasons and a lot of emotions later, I can definitively say Defiance has found it's groove.
It's not going to hold your hand. This is in the day of the life of kind of drama. The show wants you to get the sense that these characters really feel, and have their own inner demons. Just when you think someone is an unabashed hero or villain without any dimension, the show begins to peel away at the outer shell and reveals multi-faceted layers.
From the whimsically religious, barbaric and sarcastic kingpin Datak Tar, his submissive yet secretly conniving wife Sahlma; Nolan the nomadic gun for hire and his mysteriously haunted alien daughter Arisa; intelligent Mayor Amanda Rosewater and her prostitute/madame of a sister Kenya who just happens to know the truest face of her clients, there is no shortage of unique interactions and dilemmas. Just when you think you know all there is to know about your favorite character, they surprise you with undeniably real and game changing actions.
The Aliens in Defiance do look human-like. So what. There is enough there to make them both familiar and yet completely other-worldly. The Linguist behind the Dothraki tongue in Game of Thrones has created some of the most beautiful and poetic languages for the major species that needs to be heard to be believed. A lot of time and thought has gone into complete religions, social structures and traditions for each of the 5 (6?) dominant species. Castithans are pale and beautiful, snobbish and cruel with severe repercussions for defying one's long standing cultural beliefs. Iratients are in tune with nature but love to fight and make love. You really must discover the others for yourself.
Special effects are here and there sometimes, but make do to progress the story along and sometimes can leave you in complete awe. And the Music? Amazing. From the Synth themes to the alien takes on well established earth tunes, it has to be heard to be appreciated.
All in all, this show surprised me, and continues to surprise me with it's depth, it's pain, and it's humanity, even if the world is completely alien to me. I never felt this honesty with Stargate, or even my fav, Farscape. With the exception of Ben Browder, they still felt like actors playing a role. These characters inhabiting Defiance seem like neighbors. With mix matched tech and the willingness to end you if you get in the way of their survival.
Give it a shot. Be defiant stop listening to the sore losers.