What is the big deal about DX10 and building for it?

OK, so maybe I’m just missing something here, but when I build a computer and someone asks me about DX10, I just tell them not to even worry about it. My reasoning is this:
· First, it requires MS Vista, which is already overdue and not released yet--who’s to say it won’t be delayed more?
· Nobody seems to know exactly what it will be or require.
· In order to take advantage of whatever it will be, whenever it does appear, you’d need an application written to exploit the features. At introduction it’ll only be a couple of games, and then it’ll probably be a while before most gaming code writers fully embrace it. Meanwhile, traditional and everyday apps won’t have any need for it at all.

I figure it’ll be a year before even hardcore gamers have any use for it, by the time Vista makes it out and any games are structured around DX10. It’ll be a solid 2 (maybe 3?) years or more before it reaches any kind of “mainstream” level, as most of those who do choose Vista still aren’t going to have much use for the applications that utilize DX10.

I realize there are going to be the hardcores that want to be “first on the block”, but for most systems I build (including gaming systems), I just tell people to figure they’re going to upgrade their video card in a couple of years anyway; they might as well get something decent now and plan for the day in the future.