It would be silly not to go Vista. All programs in the future are going to utilize 64bit and vista is prepared for this. PLUS, DX10 is available through Visterrrrr
Yes I totally agree with you, the problem is, 64bit will not be the standard platform anytime soon. Consumers only drive a small part of technology business, where enterprise solutions (companies that buy 10s of thousands of computers) aren't just going to up and upgrade because they think its going to be the best. The market doesn't work like that. 64 bit has been around a lot longer than you think, Unix and Linux have been doing it for years, and OS X had pseudo 64bit support in their last OS, which came out almost 2 years ago.
XP has had 64 bit support for a couple years as well, if you downloaded and ran the 64bit service pack. Notice how the market has not shifted anywhere near 64bit platform yet. Only some have shifted and even then they are including libraries for both 32 and 64.
Now, given that and the fact that Vista offers no real performance increase over XP, and DX10 gives slower frame rates, and Vista offers no real benefit or feature that end users really want, I don't see it worth the upgrade at this point in time. On top of that, Vienna, which is slated to come out in 09 or 10 will have all those features that Vista had to drop, like EFI support, ZFS and sshfs, etc. and will most likely actually be more stable and offer more of a performance increase over Vista, why not just wait till then. We all know MS has a history of writing crappy OSes and bloated applications. need I bring up windows ME, or Win95 rev A, or Win 98 first release? The 9x kernel was ultra crappy and they no longer use it, they use the NT kernel now which is a lot better, and have finally made the NT kernel into a decent OS. Windows NT workstation sucked majorly, which is why it never was seen in consumer markets until XP. You can argue that windows 2000 was the first, but in all honesty windows 98 and windows ME were on consumer machines at that given time. So, it really wasn't.
So, if you wait two years you can get MS's newest OS, with all the features they had to cut from Vista, and they will be using the same kernel as before which will be far more improved. Hopefully they won't feature limit this next OS release.
If you don't have an OS at all, then I can see Vista being a more viable buy. If you have XP, in my mind don't waste your money upgrading. Wait for Vienna and all the cool technologies that will come with it. EFI will completely change how hardware works with both the user and the OS.