In reading the SRM 5 release notes I came across an interesting and unexpected limitation that may reduce the viability of VMware Replication for some customers:

Large Disks Perform Full Sync Unnecessarily

When disks larger than 256GB are protected using vSphere Replication (VR), any operation that causes an internal restart of the virtual disk device causes the disk to complete a full sync. Internal restarts occur any time:

• A virtual machine is restarted
• A virtual machine is vMotioned
• A virtual machine is reconfigured
• A snapshot is taken of a virtual machine
• Replication is paused and resumed

The full sync is initiated by ESX, and any resolution to this issue would involve an update to ESX. These syncs involve additional I/O to both the protected and recovery site disks, which often takes longer than the Recovery Point Objective (RPO), resulting in a missed RPO target. To avoid this issue, use smaller disks.