I've been in software development, focused on Microsoft, for over 20 years. The challenge my companies have always struggled with is how much change (pain threshold) can the customer tolerate before they decide to consider switching to another platform? There is no straight answer, but the general consensus is when the pain of sticking with the platform is nearly as painful as switching to another platform (give or take 10-20%) they will look at other options.I get the sense from my personal experience and what I have seen in demos that many casual users will struggle going from XP or Win7 to Win8. Power users should be able to make the transition a little easier, but not painlessly. That means almost all users will have some kind of challenge adopting Win8. By contrast, the upgrade from XP to Win7 was pretty intuitive and relatively easy, almost effortless. In my personal opinion, that does not bode well for Microsoft.Adding even more to the migration challenge is the touch interface versus the mouse. Old habits die hard, but more importantly, new habits are much harder to make. When Apple and Android developed the touch interfaces, they were specifically for small, portable, phone use. Touch doesn't work well all when it comes to precision work, which makes authoring of content on anything other than a mouse-based OS extremely intolerable. This is akin to the initial switch from DOS/Text to GUI based. Eventually the GUI won, but that does not necessarily mean touch will prevail over mice.