We all fear change, but it's looking good so far!
One thing that is already good is that when I receive e-mail alerts for new pm's, their content is shown in the e-mail, so I don't need to log-in only to find out someone has said 'Ta'!
as long as we can turn them off for mobile only, (we never had them on the old forum). Mainly as width isn't ideal and most signatures take up a full screen ;-)
You can always enable the Desktop view in your browser menu.
or a compromise would be to allow them to be enabled in the profile view (clicking/ hovering on the name/icon)