According to Configuration Guide (all releases) the usage of class class-default in a policy-map is unsupported on these switches.
In the document "Cisco Catalyst 3750 QoS Configuration Examples" (Document ID: 91862) it is used.
I have tested it and it seems to work as expected.
Anyone who has experience with this? What is Cisco's position?
There are situations, where it is *very* difficult to work without class-default.