I have been using assembly in C++ because it is the only way that I knew of to use direct ASM without using something like MASM and having a DOS Emulated interface. Basically I have been making WinApps to control hardware, like 20x4 LCD displays, motors, etc. Since I know how to control them in assembly I figured why not use C++ to add a nice GUI so that I can control the hardware without having to stare (not that I don't like the asthetics) of the DOS Emulation screens... Bad enough I use edit/notepad to write the ASM... That and I like using the Tab control, Animations, and a nice GUI :p
As for wanting to do the same in managed .NET code, since I don't really know the difference between managed and unmanaged, so I can't fully answer that question (I'm not a professional .NET programmer). I'm used to VHDL, ASM, etc hardware languages. I've only recently been learning VB/C#/C++ trying to soak all of them up at the same time :o I'm finding that for what I do C++ is the best but I'm becoming very partial to C# for leasiurely programming...