Even though this thread was created mostly for a laugh (and I got a few from some of the replies) there is still a message we can take home from this...
There are plenty of bloody good reasons why all those developers are still using Direct3D for their game development, the main overall one being that DirectX is a very good API - yes it has it's faults (as does everything in the world of programming), but considering it has to enable input functionality, graphical rendering and more for thousands of different hardware configurations out there for thousands of different style games, it does a pretty darn good job.
It also has the added support from the tonnes of documentation on it on the internet as well as support from Microsoft experts if required, as well as the fact that it was largely created by Microsoft themselves whom also design the operating systems that basically all of our games run on - an obvious advantage from a technical understanding viewpoint.
So, whilst the AMD proponents run amok on these forums shouting from the rooftops about how terrible DirectX is, just remember which API has supported PC gaming all these years and will continue to do so for years to come. If it weren't for DirectX and it's continual (albeit, a little slow I admit) development, I doubt PC gaming would be anywhere near as large as it is today (and thus Mantle likely wouldn't have ever been created). Also remember that both Nvidia and AMD pledge their full support towards DirectX and continue to do so with DirectX 12, a testament to the fact that DX is a very good API.