Wow, this thread has been a fun read. Not because of the blatant fanboyism, or the supremely amusing yet subtle trolling, but because everybody seems to be missing the point here.
Both sides have lied, neither side is innocent, this isn't a win for AMD nor a loss for NV, but most importantly (and I'm putting this in all caps for emphasis, not because I'm yelling) :
NOBODY BUYS A GPU THINKING "THIS IS GOING TO BE THE BEST CARD IN A YEAR." You buy for the now and hope that it'll hold up for a year or two(or longer, depending on your build cycles). Nobody can accurately predict what the tech front holds in the next few years. Sure, we all have an idea, but even the engineers that are working on the next two or three generations of hardware at this very moment cannot say for certain what's going to happen between now and release, or how a particular piece of hardware will perform in a year's time, whether the reason is drivers, software, APIs, power restrictions(please Intel, give up the 130W TDP limit on your "Extreme" chips and give us a proper Extreme Edition again!),etc., or something completely unforeseeable.
TL;DR: Whether NV lied about its DX12 support on Maxwell is a moot point, the hardware is already in the wild. I would be extremely surprised if, by the time we have at least three AAA DX12 titles, today's current top-end cards still perform on-par with the top-tier cards of the future that will have DX12 support. As far as DX12 stands right now, we have a tech demo and a pre-beta game that is being run as a benchmark. Take the results with a grain of salt, and only as an indicator of how the landscape might look once DX12 is widely-adopted.
And now, before I get flamed to death by all the fanboys, RM OUT!