How to figure out why VS hangs?

Suggestion from a work colleague - when VS is very very slow or is hanging:

Open a second copy of VS and attach its debugger to the first copy. When the first copy hangs, pause it in the second copy and l开发者_如何学运维ook at the call stack..

I thought it was a cool idea... but would am I missing something here? Are there any pitfalls with this approach? Or does anyone have an even better approach?

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This is a completely reasonable way to determine why Visual Studio, or any other application for that matter, is hanging or unresponsive. I used it frequently when I worked on the Visual Studio team.