Useful as in useful for knowing whether the successor was better than the predecessor. Without this information, you cannot fairly assess whether the changes where worthwhile, given the inherent cost in breaking established workflows for current users.
It's not possible to make a fair assessment without doing this because users (read: you) are biased towards what existed regardless of whether the successor design may actually be worth adopting.
It's not possible to make a fair assessment without doing this because users (read: you) are biased towards what existed regardless of whether the successor design may actually be worth adopting.