I've upgraded two systems to Windows Vista over the past few months, with vastly different results. The first was a nice ultraportable ThinkPad X60, with 512MB of RAM and integrated Intel GMA 950 graphics. This ran Windows XP perfectly happily, and became a favourite for its light weight, useful docking base and exemplary build quality.
Then I bunged Vista Business on it, instantly rendering it unusably slow (don't try Vista with less than 1GB of RAM, it's not worth it), and running into a number of driver problems — in particular, I could no longer use my Orange Option Globetrotter Fusion 3G datacard (see my previous posting). This once-cherished notebook has languished for a while, and is now awaiting a new lease of life courtesy of Ubuntu Linux. Not, I imagine, what Microsoft had in mind when unleashing Vista on the market.
The other system is a dual quad-core Xeon workstation with 4GB of RAM and an ATI Radeon X1800 graphics card, which again initially ran Windows XP. This, funnily enough, shows off Vista very nicely — especially as it's attached to a massive 30in. monitor. In fact, this beast barely draws breath running Vista, so I'm planning to install VMware and run a whole bunch of OSs, just for fun.
For most people, of course, Vista's inability to run on low-spec hardware (at least with all the bells and whistles that make it worth running Vista at all) will be the biggest turn-off. This, and the increasing maturity of desktop Linux, could make 2007 something of a 'tipping point' in the desktop OS market.
If you can get your hands on a 'f**k-off' Xeon workstation with 4GB of RAM and a 30in. display, Vista does look quite nice though.