The problem with disruptive upgrades. People don't upgrade because they don't want to move back into the "suck zone". You have to make it easy to upgrade because users will remember the pain of this upgrade when it comes time for the next one. An upgrade should be worth it so you need a good balance between "upgrade pain" and "added value". (Taken from <a href="http://headrush.typepad.com/creating_passionate_users/2006/09/why_they_d... they don't upgrade (and what to do about it)</a>).