New AeDebug functionality in Vista
Perhaps jumping the gun here as the official doc still hasn't been posted yet, but soon, I'm told.
In a nutshell, Vista's debugger support will include some additional functionality to let you customize out AeDebug works. Specifically, if "Auto" debugging is enabled, you'll have a way to exclude specific processes from being "auto debugged". (See the "Auto" value under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug)
This feature came from the need to exclude DWM.EXE from the "auto debug" mechanism. In Vista, DWM.exe is responsible for the display graphics, so if it crashes, there's no way for DWM to display the dialog that JIT debuggers show. DWM.exe is just one process where it makes sense to do this, but you can add other processes with a simple registry addition.
The really cool thing about this topic is that my innocent inquiry lead to the developer and a doc writer getting involved, and soon you should see the official description of this behavior in MSDN2. I'll post the link once it's up.