AnandTech take a further look at Windows Vista:

If your memory usage under XP kept you just under needing more than 2GB, you'll need 2GB with Vista. We took two identical installs, one with Windows XP and one with Vista, both equipped with 2GB of memory and ran the following scenario on them: We opened 104 images in Adobe Photoshop CS3 from our recent trip to Las Vegas for CES 2007; with all 104 images opened and loaded, we then timed how long it would take for Microsoft Word to start. In Windows XP, despite some swapping, Microsoft Word 2007 started in just under 8 seconds. On our Vista test bed, starting Word took almost 20 seconds due to constant paging to disk. The only difference? Vista's heightened memory requirements took a stressful situation that worked reasonably well under XP and made it far more painful with the same amount of memory. We then upgraded the Vista machine to 3GB and ran the test again; thanks to faster application load times and intelligent prefetching, Word started in 1.31 seconds. If you thought that 2GB was the sweet spot for Windows XP, chances are 3GB will be the new minimum for you under Vista.

Among those that won't become switchers, Microsoft's own worst enemy is itself, as it needs to prove that Vista is a worthwhile upgrade to XP when XP is already so refined. For many users in the consumer space, Vista is simply a version of Windows where (to borrow a quote from Field of Dreams) "If you build it, they will come." These people will get Vista on their new computers and they'll like it because it is good, but having never had the chance to decide if they didn't want it.

For everyone else who does get a choice, more often than not we believe the choice will be Vista. As we've stated before it's not perfect, but it's quite good. There are some very good reasons not to use it in some cases (system requirements, compatibility, and OpenGL performance), but for those machines that the above do not apply to, there are numerous useful features in Vista that warrant an upgrade if you find that you're the kind of person that will use them. Vista's SuperFetch and Search technology are both reasons enough to migrate from XP, as they easily improve productivity and performance.