Well, I haven't tried RC1; still, I gave beta2 a spin some time ago.
I also gave AIGLX and XGL a spin recently. I also gave Firefox 2's beta a spin, too.
So, let's take a Dell mid-range PC, with all-Intel hardware and integrated graphics - but still dual-core and 64-bit capable.
Aero Glass don't work on it. AIGLX works out of the box at full speed, though. I even made a 1999 TNT work with XGL. Save 200$ (plus 50$ for Vista Premium).
You need at least 2 Gb of RAM to forego slowdowns in Vista. 1 Go is more than enough for GNU/Linux. Save 30$.
You need to purchase the new Windows to get DirectX 10 support. You merely need to update your Mesa libraries (included with Xorg anyway) to get the same functionalities under OpenGL: direct hardware access, GLX updated in version 7.1. Save at least 150$.
You have to deal with authorizations - and learn about them - in Vista. It's part of install with Linux, and flexible systems already exist (kdesu, sudo etc.). Save time.
IE7 uses sandboxes. A Linux user account already is a sandbox. Save on antivirii runs.
IE7 provides anti-phishing. So does Firefox 2. Ff2 also provides a nice source viewer, XHTML support, real XML parsing, SVG support. Save on an extra IE theme (15$?)
Meaning that right now, considering I'm using a 'normal', paid-for version of Linux (which includes an office suite, a graphics editor, and advanced CD/DVD/MMedia tools built-in) which cost me $50, you'd need to pay me:
200+50+30+15-50 = $345 for me to consider Vista instead of an editor phone-supported (not OEM flaky answers) Vista version, and I'll want MS Office and Photoshop thrown in for free for good measure.
I'll go back to my CPU-saving, memory frugal, too fluid (I had to put a break on the FPS, it was sickeningly fluid on my FX5200), fully equipped, well designed, cool looking 3D transluscent desktop now.