Are you sure the "hackers" are all "ace programmers"?
Given that even without the source they can crack all software's security and DRMs within months (usually weeks) I would not dare to say they are all pussies either. And in case you haven't noticed, they to it for free already.
If Microsoft can't keep a stable of ace programmers happy and truly productive how will working for free do it?
And you say this in a place full of volunteers that "waste" their time doing techsupport for a product that isn't theirs? (a better techsupport than MS's own if I might add)
I mean, really?
Most do it to feel cool and to get more experience doing something they find fun. For hackers is basically the same (yes, it's people that enjoys writing code and using terminal/console commands, difficult to understand them). Give them a chew toy and they will jump all over it. And Windows is and has always been the mother of all chew toys in this field.
Who will that be and won't their interests float to the top rather than yours?
Most serious projects require the users to sign in and leave their signature on the additions/changes they made (safety reasons). And you know how are humans when competition kicks in... It becomes a community just like sevenforums.
At least with Microsoft you can vote by buying or not buying their product. If the product is free, your using it or not makes not one whit of real world difference.
Open-source does not mean "free". It just means that everyone can see the code. A lot of open-source projects actually protect the code with GPL licences to avoid copycats, MS can make a licence to protect their code. (and you can bet your backside that anyone trying to copycat any code from MS will get eaten alive in court). The fact that their product is free is purely coincidental.
I suspect that will have even less impact than a complaint sent to Microsoft.
negative impact?

Seriously they don't usually care.
Microsoft lacks the resources to pay the programmers to fix and implement everything you ask, but with open-source it's more likely your complaint is heard by an idle programmer ready to do it for glory and lulz, just like hackers blow away any DRM on games for a few "thank you" on PirateBay's comments.
Then MS only has to check what code the contributors submit.
After all, it is free so you will take what is offered and like it.
Because you can always say "**** it I don't like MS's crap! I'll use the best that competition has to offer", and then go buy an overpriced locked down Mac that won't run 99% of the software you want (either games or corporate stuff), or throw yourself in the Linux jungle and at most end up with a product that isn't better than a Mac.
Are you an ace enough programmer to trust your fixes let alone anyone else?
With Open Source, you have a ridiculously huge amount of people looking at the code. The chances bad (or even malicious) code gets implemented are nearly nonexistant.
Ubuntu and similar high-end Linux distros enjoy these benefits even if their userbase sucks (number-wise) when compared with Windows.
Good luck on trying to make a decent living fixing free software for free even if you are.
It isn't the first time a particularly good rogue programmer that did something awesome gets hired by the company it was working for free.
Happens with good game modders as well (the company making the game hires them and they become part of the staff).
The "community" is actually a far better place to recruit than the standard ways, as they are usually far more motivated, and it's easier to tell who are the best guys.
If you manage to build a decent community, that is.
I will agree that some of the software is adequate and some of that is even useful but awesome? I don't think so. Apparently my standard for awesome is a good bit higher than yours.
Firefox, Chrome, Open Office and its successor Libre Office, a gazillion of very useful browser extensions, VLC are some examples of what I'd call awesome free (and open source) products.