I've seen a number of people argue that Windows Vista, in all of its bloat and cost and lateness to market, is the best argument for switching to Linux. It's tempting, and there's a lot of truth to it, but at the same time I don't think it's a good idea to define yourself by what you're not.
First, some personal perspective. I ditched Vista on my notebook some time ago and now use Ubuntu exclusively there. The whole thing went remarkably smoothly, and so far the single biggest issue I've had has been getting Flash to work in Firefox (it's not as straightforward as it looks, sadly). I haven't been able to do the same on my desktop yet, and probably won't be able to for some time, but I'm not as worried about that.
Most people who go from one OS to the other make a habit of comparing the two. It's inevitable. If you have a choice of what to run, you want to have some idea of what you're gaining and losing. It's only normal to compare Linux to Windows or the Macintosh and make it clear what you're gaining and losing by switching from one to the other. Linus Torvalds himself said this in the recent, oft-quoted interview he had with the Linux Foundation: "If you act differently from Windows, even if you act in some ways better, it doesn't matter; better is worse if it's different."
That's a big part of why Vista probably won't drive the masses into the arms of Linux. Flawed as Vista might be, it's still Windows in some form, and that in itself has a lot of retention power. Give up Windows and you also give up the support structure that goes with it -- the gurus you go to when things break, for instance. All of that has to be traded in, too.
I get the impression there are two classes of people who trade up Windows for Linux fairly readily: 1) experts, who can educate themselves without too much difficulty about what they're gaining and losing, and 2) total newcomers to computing in general, who don't have a lot of experience built up with computing to be traded up in the first place. Most of us probably fall somewhere between these two goalposts. That crowd is typically a hard sell, and needs something more compelling than "it isn't Windows" as an argument to switch.
I've said in the past that I felt, by and large, that Linux was a success on its own merits and didn't need to compulsively compete with Windows. Now, I'm realizing that competition is inevitable -- but the way that competition is phrased also is important. If you define Linux's benefits entirely in the context of Windows's drawbacks, that may be a way to get initial attention -- but you have to have more than that in the long run.
Novelist Bruce Sterling put it in a similar way in a speech he gave in 2002 at the O'Reilly Open Source Convention, "A Contrarian View of Open Source": "'GNU's Not Unix.' OK, you're 'not Unix' -- but what are you, really?" He was frustrated with that mindset, to be sure, but was no less hopping mad at the proprietary-software world for being a virus-spewing, spam-enabling monster. He saw open source vs. closed source as a case of bad-and-messy vs. tyrannical-and-horrible, but with the former having far more potential for improvement than the latter. Provided, that is, it could shed the mind-set of being, well, contrarian.
That's why all this talk of Vista being the best thing that could happen to Linux is misguided. Linux needs to be the best thing that could happen to Linux. Anything less than that won't cut it.