Most of the comments are directed to those women wearing niqabs receiving public services but this legislation also applies to those providing public services.  
I personally think I would prefer to deal face to face when required but not having had an encounter with a niqab wearing women providing a public service, I might change my mind if I ever had one and she was as efficient, polite and communicative as everyone else.  
Employment is interesting since employers have to make every reasonable effort to accommodate religious beliefs.  To date this hasn't come up because the numbers are small and most niqab wearers appear to be homemakers.    I wonder how the public would have reacted had the legislation only addressed those providing services.