Microsoft Vista is going to take a long long long time to reach the companies desired number of 200 million plus sales in home and business, mainly because people will be very reluctant to make the necessary hardware upgrade($$$$) and their current satisfaction with latest iteration of Windows XP. More people will continue to migrate to either Apple via MacMini or probably it's upcoming media center or save expense of new hardware and try Linux distro, either Ubuntu or the friendly but now controversial Novell Suse Linux Enterprise Edition or its free Open Suse cousin. Vista will eventually make an impact but not as wide as Windows 95. The next Microsoft OS will be probably be the company's last hurrah as an OS provider. By that time, it may not matter anymore. The internet will be the new OS, even the browser as we know it may be kaput.
If a Linux distro can wiggle its way into iTunes (Novell?Linspire?), Microsoft might as well shitcan the Zune and start again. Maybe Shuttleworth would buy the Zunes and develop an open source community around this player for Ubuntu?
What will be a sleeper success will be the new Office. Hate to say it but this one is a potential keeper and came at the right time. The ribbons work. Only people that might have problem adopting are previous users of older Office packages trying to get their minds around the look. If only Microsoft stop acting proprietary about document formats and get with the ODF program. The old timers might give the new Office a miss and switch over to OpenOffice.org. at least until they overcome their bias against the new Office.
Not sure why anyone would yet switch to Google's online spreadsheet/write program, probably curious geeks, high schoolers, small business users. It is not very powerful, but simple enough for said newbies, Google fans, etcetera.