For those who haven't heard of this great new functionality.
Storage Quality of Service (QoS)
Provides the ability to specify maximum and minimum I/O loads in terms of operations per second (IOPS) for each virtual disk on the VM.
Prevents VM’s from consuming all of the available I/O bandwidth to the underlying physical resource.
Supports Dynamic, Fixed and Differencing Virtual Disks.
Here is a demo of this in action. At first I maxed out the IOPs with IOMeter, I then went on to configure Storage QoS and straight away the IOP's are reduced.