I have noticed that I have extra copies of DevEnv running after closing all 'visible' instances now. Not sure what this is related to. Upgrading to the next code drop, I'll let you know if the problem goes away.
however this only works if the parent process is still running, so unless you are lucky to catch this before the parent process is closed it will not help much.
All of the devenv.exe's are children of Explorer, however, I am only running one instance. I think this not related to VA, but to InstallShield for Visual Studio that I recently installed (The process-tree was a good idea :-).
Oddly, they all show a little bit of CPU activity once in a while... I'll let you know if I see it with out InstallShield installed.