I think the discussion about whether or not Vista will perform well on Macs is moot -- it clearly does. Any Intel Mac can run Vista in all its Aero glory. The real question is...is it worth it?
I spend all day, every day on computers. At work, I've had Vista installed for almost 6 weeks now. Truth be told, I don't like it. It's frustrating to work with after awhile. Even after becoming familiar with where MS has hidden stuff (you know how many steps it takes to get to the Local Area Connection network properties? Eight!!!!!), I don't like working with it. Once you get over the glitz of Aero, which I thought was only moderately attractive to begin with, the "ergonomics" of Vista blow hard. There's no consistency to the organization of menus, toolbar icons, or wizard interfaces. There's new fancy control panels, and there's control panels that have looked the same since Windows 95 (you want a real laugh? Go look at the Install Fonts dialog. Yeah. That's the same one since Windows 3.1). There's strange colors. There's no more icons in the right half of the start menu -- where Documents, Computer, Control Panel, etc are -- which has really slowed me down because now instead of quickly recognizing an icon I actually have to read through a dozen things. You don't realize the value of icons on common tasks until they're gone, and then it's irritating as hell. Idiots.
And last but certainly not least is UAC, Vista's new security system. One word: ANNOYING. Holy CRAP, it's constantly asking to do ANYTHING. Way too much stuff is behind that UAC control in Vista -- like a ton of control panel items that really don't have a lot to do with system security. Also, even when security is necessary, it's just very poorly implemented. Take my favorite example:
Let's say you want to create a folder in Program Files so you can put uTorrent or PuTTY or some stand-alone program in there yourself for organizational purposes. You navigate to Program Files in Explorer, right click, and select New->Folder. You get (1) a UAC dialog telling you that what you're about to do will require admin rights; you click continue and get (2) the real UAC authorization box; you continue, and now you have a new folder with its name "New Folder" highlighted so you can start typing. You type a new name and press enter, and get (3) a dialog telling you that what you're about to do will require admin rights; you click continue and (4) get the UAC authorization box.
That's FOUR damn UAC clicks just to create one folder!!!! That's indicative of how annoying that system is. If it were done right, like Linux or OS X, it would ask you ONCE, and then remember that state for the duration of your folder-creating activity.
On top of the impressively poor usability, there's a lot of programs that behave weird with Vista. Certain things like FireWorks or java apps will kill Aero until you close them again. IE7 continues to be the default browser even though I've set FireFox to be the default over and over again, both in FireFox and in the Windows control panel. And on, and on, and on...
Which brings me to my main point: yeah, you can run Vista on your Mac, but if you're just using Windows to have access to a couple programs, and not to really USE Windows, then just stick with XP. I actually have a free copy of Vista Business, but I'm not using it. You get XP on there, buttoned up with all the latest patches and a decent lightweight virus scanner, and if you aren't a complete idiot it will be as secure and safe as Vista.
I never appreciated XP as much until Vista came out. Vista's an overgrown, shiny, annoying hog of an OS. I can understand some people's desire to have the latest and greatest, and by all means try it out for yourself and see if you like it -- if you can do so without buying a copy. By God, do not actually BUY a copy of Vista if you're a Mac user, there's really no reason to. XP can run anything Vista can run (for now and the forseeable future, anyway).