Microsoft is making a lot of noise with its public statements that for most large shops -- the kind that actually have portfolios of applications they have to test for a year or more before an OS migration -- the pain of jumping from Windows XP will be about the same to Windows Vista or the forthcoming Windows 7. This got to me to thinking:

Why bother with Vista?

As always, my thoughts on tech are altogether too simplistic, I'm sure. But if -- and Microsoft is earning kudos for its candor in this regard from several analysts -- Vista and 7 are going to be essentially the same code base, why on earth would a company choose to go through the expense of rolling out an OS that folks just don't like? Particularly if they are on a battle-tested XP SP3 build that will be supported, at least on extended support for another five years or so?

Just to clarifiy: Microsoft promises that Vista and 7 will be highly compatible. In fact, the Windows for your Business blog post that kicked off much of the conversation advises companies to test apps now running on XP against Vista, and to take that as a valid watermark of how nicely those apps will play with Windows 7.

There are only three plausible scenarios I can foresee to warrant a Vista rollout at this point. I gotta be honest -- I foresaw this kind of hazily until I read Mary-Jo Foley's post about her interview with Redmond's Gavriella Schuster. But it just seems like common sense to me.

• Your proprietary applications are so dated that major coding can't wait  the year (or more, based on past performance) that waiting for Windows 7 will add to the update cycle.
• You app vendors are no longer supporting XP, or more likely are releasing new, must-have versions that are dicey on XP.
• You are buying a ton of new hardware right now (hey, processors are cheap) and the added expense of XP installs -- assuming it is an expense in your licensing scheme -- is gonna be hard to rationalize for a couple years' peace of mind. (This one's a stretch, since IT is largely in the peace-of-mind business and Vista SP1 has turned out to be something of a drag, as well)

Foley surmises that Microsoft's pitch has evolved in a day or so from "waiting for Windows 7 won't make migration easier" to "just get off of XP, would you?" -- particularly since more than 70 percent of businesses still run XP.

But with a few exceptions -- surely there are more and better reasons than I listed above -- the main reason people didn't jump at Vista upgrades is they don't like it. I mean, they really don't like it. Our own CTO this morning told me that he equates Vista with the dreaded Windows ME -- an incomplete, interstitial release against a largely new code build.

With cost containment once again the most pressing issue on everybody's minds, that's two strikes. And if from a migration standpoint the jump from XP to either Vista or 7 is essentially the same deal, why hurry?