Twitter claims preventing user confusion as a motive yet the move from old to new Twitter on the web is the biggest source of confusion. I mean, come on. Teaching people an interface isn't rocket science. Do something simple, such as put out a video a week showcasing use of the new interface. Heck, have user contests to come up with videos showcasing the new interface. Or go all out and develop an awesome training and help system, and integrate it into the interface. If users have a problem, do something about it!
