I am always impressed by companies that take a very proactive approach to helping users know that they are making a change; and I’m always surprised by those that don’t.
The technology is at your fingertips, and it’s easy to use. You have your customers contact info (hopefully). Why wouldn’t you reach out and build some loyalty to your brand by making them believe that their understanding of coming changes is important to you?
from 37 Signals, a product that we’ve used for a couple of years now, does a great job of just that. They regularly post notices where I will see them that inform me about coming changes, upgrades, etc. That has done so much to build loyalty for me with their product because I actually feel like they care. Even the survey that I took was a great experience, because I truly felt like my voice would be heard. (And strangely enough, it was! They implemented at least 1 of the changes that I thought would be a big improvement)