Is vista good: yes.
Is Vista worth the money: maybe.
I bought a new PC with Vista on it and I love vista. I'm no stranger to windows computers, though I am more biased to mac. However Vista gives me faith in windows again. I have XP, OSX, and Vista and my vista computer has gotten all my time (and not just because it's the fastest). I'm a hardcore gamer and Vista is able to run my game of choice (generally BF2142), my iTunes to sync my iPod, and decrypt a DVD (when netflix sends me something good).
It's just as stable as XP was for me, and I really love all the eye candy - when I hope on my XP machine I almsot miss it. It has a nice interface and feels a little like OSX - my personal favorite in the world of operating systems.
Also the ocean of problems refered to - well I haven't run into any. The annoying security features are a quick disable, and all my software installed without a problem - as well as the drivers for my video card etc. The sidebar is a ripoff of the Mac dashboard, but I'm not complaining because I like it. My personal favorite widget (or gadget for vista gents) is one showing the current threat level. (Is it just me or is "elevated" really mean no threat?).
Ultimately, if you want the cool new things Vista does then I say go for it! It's nice to use, very stable, and has the best of the Mac and PC worlds.
If you're deciding on vista or a new video card, get the video card. vista is definately unncessary in today's world ... XP would suffice just fine but If money is no issue then I would go for it. I'm glad I did.
and as far as DX10 is concerned ... well I can't nearly afford a DX10 card any time soon so I don't see game manufactures requiring DX10 for some time. My 7900 palys all my games to my liking and I don't plan to upgrade any time soon. Game manufactures would be killing their profits not making their games also able to run on DX9 systems ... theer are lots of poor gamers out there. We're called College students.