Like that one pretty witty. 
I do have them installed via Office 2007, I don’t use them myself.
I don’t have them either on my computer either, but I still use them on some of my websites 
It depends what other fonts you’re using. If your default non-Vista font is Arial, that’s a fairly similar size and appearance to Calibri, so your design should translate fine when you put the new font in. But if you’re serving up Verdana to people without Calibri, there is a much more noticeable difference in size, so you’re more likely to end up with a design that doesn’t work well with one font or the other.
That’s the reason I don’t use them on the Web, although I do use them (Calibri mostly) for documents that I create PDFs of.
Cool. Keep em coming, guys.
Edit: Logic, which site?
I do, my website uses them actively (just check the source!), I use a mixture of Constantia (titles) and Candara (body) and it looks pretty good in the end browser. Before I probably wouldn’t have advised it but since Windows 7’s release (which has it) and the degrade of XP I think they qualify as websafe. Vista, Win7, The office viewers, Office 07 and Office 2010 all have the fonts (as do the mac versions of office 2008), it’s a high enough proportion (partially inclusive of XP for office users) it’s time to begin using it (with appropriate fallbacks). My PDF resume also uses Calibri (body) and Cambria (titles) as the primary typefaces! 
I’ve been using Calibri for body text, and Consolas for monospace. And have done some experimentation with using Segoe UI…for well…UI components.
These fonts just look great, in my opinion. Even better once IE and Firefox use Direct2D for rendering.
Unfortunate, most of the sites I get to work on are only accessible on private networks. That is not to say there is a control (hardware/software) over the systems that access these sites.
The size not much of a problem when you build in a flexible way that can accommodate font size difference. Also the difference in size is nothing too concerning, couple of pixels in height here and there.
and their reliance on anti-aliasing to display properly.
At lot more tricky, however, I find them to be fairly acceptable without anti-aliasing compared with the others (Arial, Times, They are not too pretty without anti-aliasing either). Except for Consolas, its not very pleasant to read without.
You can get the Vista fonts any number of ways without having to install either Vista or Office (or even run Windows – Mac and Linux users can install them also). The issue is not how you get them, but whether you can design around their two main limitations: their size differential and their reliance on anti-aliasing to display properly.
No, seeing as I don’t use Vista (and personally don’t understand why anyone would) or Office, therefore have no access to these fonts at all.