Worst thing is coupling UI redesign with changing the set of features. First, you lose a familiar interface and you don't know where to find even the existing

Worst thing is coupling UI redesign with changing the set of features. First, you lose a familiar interface and you don't know where to find even the existing features. Then you realise that the feature you're looking for is no longer there. Maybe it will be brought back online later or will be replaced by another, "better", feature later. UI redesigns are sometimes just plain unavoidable but they should be done separately from other changes. Much like you want to commit the code reformatting change separate from functional changes so you know you're just changing whitespace basically and there's nothing that should break your codebase. As a user I can only absorb a certain amount of change at a time: I can learn a new UI if I know I'll find the familiar pieces somewhere in there. And I can accept new features or old ones being changed to different ones if I know the UI will still be the same.