Greatly improved customer service - the back office and the web store can deal automatically with almost every order and customer query.
Much faster response time.
Enhanced capacity - greater automation allows you to deal with much larger volumes of business.
Reduced costs in the medium and long-term. Although set-up will be a one-off cost, integration will save time and money in the future.
Improved accuracy - with web store and back office accessing the same data the chances of errors are greatly reduced.
Staying competitive - efficient, timely service is vital: if your competitors run a more efficient, responsive service you could lose your customers to them.
Better use of staff time - if back office and online systems stay separate you are constantly wasting staff time and resources duplicating data from one system to the other and back again.