Thanks for your insights, Jeff and Ion.

If anyone is interested in my conclusions, I wrote them here:
http://1czajnik.blogspot.com/2012/07/move-aware-classes-in-c03-and-c11.html

I will start a separate thread on the developers list regarding Boost.Move and writing the assignment operator in terms of pass-by-value and swap.

Cheers,
Kris