When people say Vista was bad, they're not talking about the operating system itself. They're talking about the user experiance and context at the time:

• Most people forget we were all on the cusp of switching from x86 hardware to AMD64. It was a relatively easy transition, but it was a jump that provided some hard hurdles (drivers) everyone had to jump together. Some things were not automatically compatible. You would likely have to throw away some piece of otherwise perfectly functional hardware to upgrade. People didn't like that.

• Also, we were also switching from single core to multiple-core computing. Software had to be written to specifically take advantage of this and often it wasn't. So even if you had the latest and greatest hardware, the performance gains were often disappointing.

• The driver models had to change because Win XP was a security nightmare for most people. Browser security had completely been neglected by Microsoft in favor of pushing their ActiveX controls in IE6 and IE7. The entire security model had to change, but the UAC prompts were absolutely out of control. Still, it really was better than getting wrecked by malware.

• microsoft pushed new file formats with Office 2007 for absolutely hostile reasons and also transitioned to the ribbon interface. These might have been technical improvements, but they were more compatibility hoops people had to jump through that they were frustrated by.

• Apple was thriving. iPods were in everybody's pockets and the first iPhone had launched at exactly the same time and was changing how people thought about computers. Vista was "more of the same" in all the wrong ways. Where was the innovation? Gmail launched in 2004, why couldn't Microsoft make a competing offer?

• Finally all the cool, futuristic features that had been hinted at with Windows Longhorn were cut from Vista. If you were someone who followed those things, Microsoft over-promised and under-delivered.

Ballmer-led Microsoft had mismanaged their core products for years and it all came to a head with Vista. The consumer frustration was palpable and coincided with several architecture and forced UI changes that really made it hard for people to fall in love with Vista. Individually each problem wouldn't have been a deal breaker but swallowing all the required pills at once left a sour taste in people's mouths and had them looking at alternatives. It's no coincidence that macbook and netbook sales rose sharply over the next few years.