I think you'd be better off using alpha readers, or a writing partner for this. Or, hell, even SYW so long as you've proofread for grammatical/punctuational errors.
I also use an alpha/beta system, which is pretty similar to the testing systems Maryn mentioned, though I'm less thorough than most tech studios.
I need someone I trust intensely to look at it first and find anything I've said that I should not have said (bad sex scenes, faux pas, really offensive description or inappropriate mythological appropriation). This really helps with my nerves, and it lets me write that first draft with a clean slate to take any risks. I can count the people I trust to do this on one hand. They would not fit the objectivity bill, but I don't expect them to or take their feedback that way. They're closest to writing partners. I know their tastes, I can get a pretty good sense of their biases, and so on.
I'm also a pretty stern self-critic. Maybe too much so sometimes.
Then I use betas and critique to find those things the alphas wouldn't tell me or that I've gone blind to. This always turns up a lot more than I bargained for but I operate with a couple of rules. First, betas don't write my book--that means I don't take plot suggestions or drastic character personality changes from them; "character doesn't feel like someone who would say that" is fine, "character would say this instead" is out. Both of those statements tell me the same thing: character isn't right in this scene for one reader. That leads to the second rule: I tabulate all suggestions, cross-reference to the alphas and other betas, and dive in to diagnose the problem.
I used to allow critique earlier because I find when I leave it so late I run the risk of having too much committed to the story and I end up not wanting to make changes. I had a few really bad experiences sharing work that I hadn't been able to pick apart myself first. I found that I wanted more understanding of my own piece before I had to consider why it wasn't working for someone else. I need to know what I did to fix what I did, if you know what I mean.
I may change this, though. I've learned a lot about testing games recently, which came with a bunch of background about how unbelievably awful we are at saying what's wrong with something. We invent reasons and don't know any better. The only thing we can learn from a test is that something didn't work. The best example of this in action is the (award-winning) video game
Gone Home, which is a really cool piece of experimental interactive narrative that's flawed in all kinds of wonderful ways but never the ways any of the myriad reviewers who hate it ever give. People can play the game, fail to get the atmosphere and point of it at all, blame the controls and dialogue, and the problem is actually caused by unspoken narrative created by the skybox, the sound effects, and the level design. That whole effect is, arguably, what the game set out to experiment with. To actually analyze it you have to almost turn your brain off or else your inherent biases about what games are or are not will entirely influence what you think is wrong with it.
