Functionalities and layouts are changed every so often due to a number of reasons, notably including much customer feedback. If there are common themes found in the responses from our customers, we take note and try to implement them where possible in order to improve the service. Of course, not everyone will respond to the changes in the way we would hope, however, we are open to amending issues that crop up after users have had a chance to work with them.
I make a point to remind customers to check the Preview area every so often, so that they have the opportunity to test any upcoming changes and send us their thoughts and suggestions before they are deployed. Changes are usually in Preview for a month before this happens.