Yes, there's a new desktop window manager, but no, I don't know any more about it than you do
Sean W. requests, via the suggestion box, “an in-depth discussion of the use of the shell’s new Desktop Window Manager (Dwm*) functions in Win32.”
The desktop window manager is not actually part of the shell. It operates at the window manager level. (Notice that DWM is active even when Explorer isn’t running.) You probably should have posted your suggestion to Greg Schechter’s request for DWM topics which was not too old at the time you posted your topic suggestion. But then again, “Best practices for applications under the DWM” was on his list of future topics, so it looks like what you wanted was already on his to-do list. I don’t know whether he followed up on his own to-do list, though. If not, you can always consult the Performance Considerations and Best Practices (for using DWM) topic in MSDN.