Restricting yourself to a single API is foolish. This foolishness can be avoided by designing your engine properly so that you don''t need to choose one api over the other. Everything is abstracted at a lower level, so that all you need to do is create a .dll file or similar to allow the engine to switch between API''s. Obviously this is a bit to advanced for "learning" purposes. Which is why I said to learn 3d theory, and work on your engineering skills. You should be able to easily implement such a design once you know the 3d math, and have the engineering skills that make it possible.

And the rest of the "help microsoft" "save linux", "cross platform" talk...is just talk. With a good engine design cross platform capabilities are as easy as pie. And as for helping microsoft? Well come on now...I suppose you thought about "helping microsoft" when you installed the windows OS, or DOS, or Office, or when you bought an Intellimouse, or a MS keyboard, or an MS Joystick. You can hate them all you want, but designing a few apps to use directX will not help or harm them in the least.

Final words. Like I said before, learn the theory. Then if you want to learn a specific api you can easily figure it out in a short ammount of time. And perhaps by then you''ll also have a better idea which API suits you best. If you want to make a game...well I highly suggest you spend along time designing the engine so that it can support any API or extension that may come out. This way you won''t have to totaly re-write the engine every time a new video card/API/Extension comes into play.