There are plenty of successful websites out there using this navigation layout, so it not all bad or all good. I personally am against it, an here's why. It violates visual hierarchy. With the nav above the site name (and/or) tagline.
With the traditional layout, the nav is clearly a child, and the logo and page name are clearly the parent item. Clearly indicating to the user that these buttons will move you around the parent site.
Traditional

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With the nav on top layout style, it is less clear that the nav is a child of the site name, and not independent. For example, I as a user may think that this is an inter-site nav (like the top nav on google, or cheeseburger network); rather than the normal intra-site nav.
Your Layout

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If you must put the nav above the header, here are some alternatives to consider:
With this one the containers are organized so the nav is still the child, but its still less clear.
Alternative 1

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Or you could do something like TechCrunch and keep the logo inline with the nav, which works very well and is quite clear:
Alternative 2

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Lastly you might consider just putting the nav below the header, and on user scroll, fix it to the top of the browser.