I was a littled puzzled about the differences between DX6.x and DX7 until I read this from Tim Sweeney:

"The API's simplicity has also improved, which is something you don't often see: usually code just gets more complex as it evolves. Porting Unreal Tournament's code from DirectX6 to DirectX7 only took 3.5 hours, and mostly consisted of deleting now-redundant code and changing function calls and interfaces. I'm very glad to see the IDirect3DTexture, IDirect3DViewport, and IDirect3DLight interfaces gone, and replaced by much simpler state-setting code. Direct3D's abuses of object-oriented programming are now gone."

What an insightful dude!