DirectX 9 is a bit old now. I realize it is still very much in use so the article might be relevant for some, but from my perspective it would be great if you could write an article about DX10 or DX11.
What is the difference?
Are there keyword changes?
Has the whole structure changed?
Will anything created with directx 9 still work with directx 10?
If this "Primer" was written for DirectX 10 what would the differences be?
There is a lot of difference. One major being more use by dropping the ugly fixed vertex format and going with shaders only. There is DX11, which from what I heard can render for DX9, DX10 and DX11.
A lot of it has changed. I personally don't know DirectX has I haven't used it in a long time. But I don't see the point of wasting time (imho) messing with DX9 unless you want to support those XP users who are too lazy to upgrade to Vista or Windows 7. By supporting them, you waste functionality due to the limitations.