I wrote several MBV samples long back. But I have really fascinated by Delegator stuff of Keith Brown and later of Don Box. I wrote my own MBV Delegator in order to learn how to write delegators based on Don Box's implementation and added stuff to generate trace output using the ITypeInfo. For thunking, my approach is like ATL's. click here to download.
If you are in love with ATL and want to implement MBV based on PROP_MAPs check out Chris Sells' MBV implementation.