Its always supported OpenGL, the debate was over if they would stop support over newer versions.

I'm not a mac guy but I didn't think it's GUI used 3D technology for it's OS? Maybe I'm wrong.

Anyway, I will not buy Vista. I usually skip an OS with MS. Had 98, didn't buy ME, and got XP. I alos think it's OK to have high specs. I want a high tech OS like on that Tom Cruise future type movie where you move everything with your hand, and I would imagine it takes a powerful computer to do that.

OK. Seems hard to compare Apple and MS. Apple is really the whole PC along with the OS. MS if just the OS, so they don't know what the user has for hardware. If MS was like apple in that they had the hardware and you had to use that, they would be sued again I'm sure.

[EDIT]
Also, are they truely using the full force of that hardware acceleration? Some of the screenshots I've seen on vista look like they are using 3D window searches or something. Just because they use hardware acceleration to draw windows doesn't mean they are using all 3D features for their OS?

I see no difference since they use the exact same hardware. Only the earlier versions of OSX were runnig on Power CPU but that hardly matters.

One more interesting thing is that I can use XGL/AIGLX on my ancient gf2 mx with 32M of vRam on P3 500Mhz with 256M ram. Compare the features of compiz and Aero and their HW requirements. Something seems awfulyl wrong with Aero's HW requirements.

Quite true. That's no reason for Vista to require more powerful hardware than OS X to do the same thing though.

I don't know, but from the hardware perspective it shouldn't matter if it looks like 3D or 2D to the user. It uses OpenGL anyway.

EDIT:

No, but you can go there and buy the same graphics card as in the Mac and put it in your PC. Well, you probably could plug any random graphics card in the Mac, but I would expect it to fail horribly since it's not what the OS was designed for.

From what I know, Mac GPU's simply have a bit different BIOS loaded. You can flash it to become a PC GPU and vice versa.

Isn't that what drivers are for? You know, they should make programming HW a bit simplier
Besides, games have been running on all sorts of HW without too much problems. I bet Apple and MS have lot more recources to make their software working on different HW.

Ok, let me ask a bit differently:
what graphics HW does Apple support with OSX?

Am I correct when I say anything from NV and ATI starting from FX and 9000 series and later Intel integrated video? Or do you seriously think that OSX on Mac Pro only supports 7300GT, x1900XT and FX4500?

You can buy mac's from Apple home page with different kinds of NV, ATI and Intel integrated graphics. I would assume they are all officially supported by Apple.

Well, Vista actually seems to support about as many GPU's as OSX, perhaps even less assuming that OSX works on pre-DX9 HW too
Also there are very little difference between the GPU's of same generation (e.g ati x8xx, NV6xxx)

What is different about them besides stickers, coolers and in some extreme cases, board layout? They all use/work with the same drivers the GPU manufacturers provide.

Can you bring some examples where graphics cards manufactured by different companies that use same GPUs work differently?

Only affects speed

I don't think they can disable features that affect window manager HW acceleration (ooh, let's disable vertex shaders to save some money! ).
Only all sorts of IO ports and perhaps some de/encoders could be disabled/removed, assuming they are in an addon chip and not built into the GPU itself.

Let me remind you that this discussion started when someone said that perhaps it is easier for Apple to provide desktop compositing since it supports only a few GPU's. I tried to explain there really is not much differece, certainly not in programming and API end.

That's why they should replace coolers also. In any way, OS doesn't have to take care of bad HW and from what I know, no OS tries to. Worst that could happen is that drivers lower clock speed and voltages to reduce heat, OS itself has (almost?) nothing to do with it.

When Intel IGP is enough then any other GPU is enough for Aero also. After all, that IGP uses system RAM (very little throughput) and half the stuff is calculated on CPU. Only minimum requirement I've seen for Aero is DX9 compatible HW with 128M of vRam, no mention of memory bandwidth or shader power.

They can and do with modified BIOS. Driver takes care of everything else and you won't need a special driver for your crippled GPU to work, the official ones will do just fine.

But still, OSX should work on two completely different CPU architectures
Also, if I'm not mistaken then OSX works with G4 CPU's too. IIRC, by todays standards they had some very low-end DX8 class GPU's back then.