Hi (again) Ion, I recently ran into the following issue. I defined a copyable-and-movable class X, and class Y has a member variable of type X and no other member variables. It thus (apparently) happens that Y's auto-generated operator= takes a non-const reference to Y, which I would guess is generally not desired, or at least an operator= overload taking a const reference to Y should be available. For whatever reason, MSVC9 didn't complain at all about using the auto-generated operator=, but when a friend tried compiling code with GCC on Ubuntu, GCC complained about no matching function call to operator=(const Y) (or something like that). The error occurred within a concept checking class, and I would've assumed that MSVC9 was looking at the same code and should've come to the same conclusion; I haven't investigated this further. In any case, we added a trivial Y::operator=(const Y&) explicitly, but GCC didn't like this overload, and it finally quieted down once we added *both* Y::operator=(Y&) and Y::operator=(const Y&). Unfortunately, MSVC9 gives warnings about several operator= overloads, so right now we only have those explicit overloads of operator= when compiling with GCC. The only point I want to make is that it seems worth mentioning this subtlety (at least it was a subtlety to me) in the move documentation somewhere, and perhaps how to most easily and portably address this (I'm not sure what that would be), as I would expect it to be a not uncommon situation. - Jeff