ActiveSync is fast becoming the default email syncing protocol. Windows Phone, Nokia, Android, iPhone, Blackberry (AstraSync) . Blackberry requires additional hardware and licensing to function. BES has a one device policy, ActiveSync doesn't. Exchange ActiveSync scales easily, especially with Exchange 2010 DAG. The increased IOPS that Mark refers too has major impact for large customers. One of my customers had to upgrade their SAN to cope with the increased BES traffic.
Cheers Wayne
Airloom