One of the big concerns everyone would have over Nokia's switch from Symbian to Windows Phone is the cost. Windows Phones are known to cost significantly more than their Symbian counterparts. However Nokia has promised that their Windows Phone devices will be cheaper making it an easier transition for the Symbian smartphone users.
Since Microsoft has been strict with the Windows Phone hardware in this iteration of Windows Phone, we will have to wait and see how cheap the new lineup of devices will really be.