Having used WinDBG for a long time to look at stack traces after a process has crashed or hung, I am glad to learn about this new tool in this Channel 9 video starring the Developer Solutions Team. Here's the link to the Powertoys blog as well.
The Managed Stack Explorer lets a developer look at the stack of a Managed process and debug it live. Best of all it does not require that the process be killed in order to detach to the debugger, which is probably the biggest pain with using ADPlus. Those critical production systems that have intermittent problems can not always be brought down in order to get a good dump file.
The only catch with this tool is that it only works for .NET 2.0 components, but it'll be very useful in the near future I bet.