Not a lot, actually, but perhaps enough to straighten out some confusion about what it will do for games, including Flight Simulator. In the couple of weeks since we made our new product annoucement there's been much speculation and, having been surrounded by information on Vista, I neglected to consider that not everyone in the outside world understands as much as I pretent to. ;)
What is Vista? Simple. It's the next major version of Windows, just like Windows 98 and Windows XP were major versions Vista is a MAJOR version. It's a new OS, baby!
What do I need to run it? Like current versions of Windows you'll be able to by a copy and install it on the PC you have. PC manufacturers like Dell, Gateway, Toshiba, etc. will also pre-install it on new PCs. I don't know if you'll have a choice of XP or Vista when you order. It used to be you could choose between Windows 2000 and Windows XP on new machines right after XP came out but now pretty much everything is XP.
Why do I want it? Why do you ever want a new OS? Because it provides the foundation for the way you use your computer, including the programs you install. Vista offers a bunch of new features like an improved UI and better security and stability. Probably one of the best things is that security features like limited access user accounts and anti-spyware and anti-phishing technology will come standard. The search capabilty kicks butt if you've ever misplaced an email or document file. Plus, the new UI is very cool and is now fully 3D--meaning it's rendered using 3D APIs just like games are. Finally, running games on Vista will be much better than XP since you'll have a central place to access your games (including saved games) and for those of you who own other games besides family-friend Flight Sim <g> there is built-in support for parental controls tied directly to the major game rating boards such as ESRB, PEGI and CESA.
What's all this about DirectX10? Hopefully by now you know what DirectX is--a software layer and API to exploit the graphics, audio and other game/entertainment features of your PC. Well, Vista will include the next generation of DirectX--Direct 10 (a.k.a. DX10). The current version is DX9 and it's available on Windows XP. Vista will support both DX9 and DX10.
Why both? The biggest reason is that DX10 will not work on currently available graphic cards. It's just changed too much to be compatible--at least that's my understanding. And since Microsoft wanted you to be able to run Vista on the PC you already own that meant including DX9. In fact, the new user interface is written in DX9. DX10 will be there for programs that make specific calls to it. For a game like Flight Simulator that means first checking the OS and DX versions and then deciding which functions to call.
What's the big deal with DX10? DX10 is a complete rewrite of DirectX. That in itself is a big deal. The rewrite now treats the 3D graphics system much like the memory or CPU on your computer, meaning the core OS manages things like resource sharing and scheduling. That's just a fancy way of saying that the stability and robustness of the graphics system will be as good as the core OS. Remember the bad ol' days of Windows when an application crash might lock up your PC? Windows NT (and subsequently Windows 2000, XP and 2003) fixed that. DX10 will do the same thing for graphics. A crash in the graphics system won't "blue screen" your PC.
Is that all? No. Not by a long shot. DX10 also promises greater capabilities and performance. One way it will do this is through Shader Model 4.0 (a.k.a. HLSL 4.0). Shaders are special programs that run on the GPU. Until now there was a size limit that caused many costly trips across the system bus to get the job done, slowing things down. Larger shader limits means less trips across the bus and thus better performance. The DX folks estimate you could see an increase of up to 8 times, depending on how shaders are currently used in your programs. The other thing HLSL 4.0 does is get rid of the difference between pixel shaders and vertex shaders, making shader programming a bit simpler. Now there are just shaders. In fact since shaders are basically massively parallel math programs HLSL 4.0 will allow for a lot for general purpose programming on the GPU. (Hint: all you folks clamouring for Flight Sim to support a separate and non-standard physics chip should really be lobbying for us to use the GPU.)
Should I get Vista? Duh. Of course. Not only will the OS be more robust, secure and useful but you'll be positioned to take advantage of DX10 games when they come out. You won't get that under XP. Of course you'll need to upgrade your video card at a minimum, but that seems like a small price to pay for better, faster and shinier games!
Yes, a new version of Windows is coming. Yes, you should be able to run it on the PC you have (provided it's reasonably new). Yes, you'll probably want to upgrade your hardware so you can take advantage of DX10, but it's not essential to run Vista. I hope this helps clear up the confusion. Feel free to comment on this post if things still aren't clear.