Microsoft's biggest enemy is probably itself. Getting users to upgrade to Vista hasn't received the kind of welcome many thought. Microsoft has tried hard to get users to switch using the "Wow starts Now!" campaign and even taking desperate measures such as launching a "Get the facts campaign against itself", similar to the discontinued "Gets the fact on Linux" but stating that XP's flaws.With all that failing, recently they started providing Vista Business and Ultimate users (aka users who paid BIG $$$) an option to downgrade to XP.
Many vendors including IBM, Dell, Fujitsu and HP are offering this downgrade option or providing XP as an option.
Given all this, who can blame users that have been stuck with XP for so long. Asking them to upgrade is like asking them to move from the home they grew up in, even if its supposedly a better and more secure home. At the end of the day M$ is to blame for dumbing down the majority of users to a point where they get nervous the second the desktop wallpaper isn't a blue sky with green hills!
This is probably where the Free/Open Source desktop users are better off. We have a desktop that gradually, but rapidly improves. Software packages update pretty much on a daily basis and most GNU/Linux distros have at least a bi annual (6 month) release cycle. Our users are always upgrading and looking forward to the next version. And why shouldn't they be?
We have a lot of things to be excited about such as the best 3D desktop, exciting kernel improvements with each release (check out the latest 2.6.23), best 64 bit computing support (make better use of Core2 Duo/AMD64), hottest Virtualization Technologies and support for an insane amount of hardware devices. To top it off, we have a bunch of "kick ass" FOSS licenses to tie it all together and provide the user with total control! What more can users ask for?
At the end of it all, I feel that though M$'s gamble to treat users as a bunch of noobs has paid off in getting them to buy into computers by the masses it is now faced with how to go about lifting off those XP couch potatoes and moving them to another couch. Till they figure out a way...long live EXPee!