One thing to note is with a WMS you will need to make sure you have someone responsible for keeping the transactions "cleaned up" each day.
For example, make sure Pick List are getting completed and fully closed, Sales Orders are getting fully shipped/closed, Inventory Counts are getting completed/approved, etc. If you leave partially processed transactions in the system it will make a very "dirty" system that is prone to lots of data errors. And it snowballs FAST! Maintaining a WMS is a lot of work that many companies are not prepared for and therefore get frustrated with them quickly. Most of the complaints I've seen with the NS WMS are because of poor maintenance of orders/data not because the WMS didn't work well.