Jason has written a great post on why Exchange Server service pack 1 affects mobile users. Summary below or go here to view the full post:

There are many key enhancements in Service Pack 1 however from a mobile perspective there are some very important additions.

With Service Pack 1 we have added 30+ new policies for Exchange Activesync.  These new policies will require a future version of Windows Mobile (similar to System Center Mobile Device Manager 2008) however they can be implemented within your Exchange 2007 environment now ready for when that version becomes available. 

There are 2 different categories of policies - the first set control the Sync, Authentication and Encryption settings.  The second set are really focused on controlling functions on the device.

Sync

Within the Synchronisation setup we have the ability to configure many of the synchronisation options on the device:
Configure message formats (HTML or plain txt)
Include past email items
Email body truncation size
HTML email body truncation size
Include past calendar items (Duration)
Require manual sync while roaming

Authentication

With the device password we can enforce more complexity as well as setting a password expiration and remembering password history
Minimum number of complex characters
Enable password recovery
Allow simple password
Password Expiration (Days)
Enforce password history
Allow Windows file share access
Allow Windows SharePoint access

Encryption

From a security perspective we can control the use of SMIME as well as whether Device Encryption is enforced
Require signed SMIME messages
Require encrypted SMIME messages
Require Signed SMIME algorithm
Require encrypted SMIME algorithm
Allow SMIME encrypted algorithm negotiation
Allow SMIME SoftCerts
Enforce Device encryption