What is the main difference between Exchange 2013 and previous versions?

If we list the point which ware not in previous exchange.

1- Touch Optimized

2-Support for apps

3- SharePoint and Lync integration

4- DLP (Data loss prevention)

There is significant changes in exchange2013 . Exchange roles are cut down. No (EMC)exchange admin center.In-place e-Discovery and in-place Hold. Integrated with lync and SharePoint.. OWA offline Access and Apps.

Exchange2013 has different architecture from previous versions

Mailbox and Client Access module

no mmc exchange management console instead web  interface management module named exchange admin center

accessible through https://domain.com/ecp