...would be allowed to answer your (good) questions, as most of what you are talking about falls under NDA. There are some historical/foundational differences between what is available to hobbyists and what comes with an SDK.

At the end of the day, the kit is very similar to the compiler on all fronts.

With XNA you use VS Express editions, which are really incredible IDEs and cover 99% of the issues a small or lone developer will need. With actual development, it is VS 2005, which by itself has super-powerful tools, customizations, plug-in interfaces and analytics...the sort of stuff a 20+ million dollar game needs to eek out every bit of optimization.

Could you use OO code under C++ using the DX library...sure. Must you? No. Most professional development is going to be built from the ground up and most will support c++...object oriented design makes sense even if you don't use GDI+ or any libraries.

XNA has one, and really only one, way to do things, and that way is amazingly simple and well thought out (now that the pipeline is here). With a straight SDK, however, you could implement a game in whatever fashion you see fit using whatever styles/tools/languages best fit your given need.

... it's much appreciated.

I agree the express editions of Visual Studio are very productive. I'd been doing most of my programming in C++ and Win32 before but after I started using Visual C# productivity went up quite a bit. The Intellisense and the C# language itself speed up coding times.

From what I've used so far XNA basically seems like a wrapper for Managed DirectX so I've been finding it pretty easy to use. If you can do 99% of the stuff with XNA then I'm pretty happy and I'm glad I won't have to spend $15,000!

Can't wait to have access to the Xbox Live interface when they release the Professional version so I can make my game multiplayer. That'll be cool!

Underrated comment. I used to hate that game so much that any time my siblings asked me to play it, I just picked Hom and shut myself down mid-match.