RaiderX said:
also vista uses a lot more resources than XP so you would need a better CPU to equalize with XP
the legacy version of DX9 is emulated as far as i know, its not always slower, but drivers are maybe not up to scratch, or they think there isn't too much point. i mean, most cards x1900 series and up have very little trouble with almost every single dx9 title, so 10fps isn't really hurting most users once you get past the fact its irritating having lower performance.
as for uses more resources, i wish people would stop saying that just because they've read it.
it uses more memory for system cache, its not a hard drive, memory can be instantly released and overwriten in an instant. it generally only increases performance.
i forget exactly how much the kernal(which is the only actual footprint that the OS must keep) keeps in memory on XP, but right now in vista 64 with a bunch of stuff open, and a high def vid playing Vista has 134mb of the kernal in memory, 83 pages, 51mb non paged. so vista on its own is using 134MB memory, hardly resource hogging or over the top memory usage. have 15mb memory free , 1.3Gb is used as cache, rest is programs i have open. its extremely responsive and flicks between programs instantly. try vista before you run around saying vista is a resource hog.
the idea behind M$ talking of speed increases, as with all advertising you can use any stats to mislead people as it is theoretically true. the idea would be, in a while if you took a game that could run in dx9 and dx10 modes but had no different effects, and gave the exact end result the dx10 version on vista would run significantly faster than on dx9 on XP. now it will be very hard to prove, and will no doubt be something they found running an incredible specific game , most likely some gaming demo that showcases every single speed increase in DX10 and doesn't use anything else that might slow it down and won't be real world performance.
see above about caching. it's all good. 
