Why use WinDbg vs the Visual Studio (VS) debugger?

Question

What are the major reasons for using WinDbg vs the Visual Studio debugger?

And is it commonly used as a complete replacement for the Visual Studio debugger, or more

Answer 1

I have used it when I've been sent .dmp files from an NT4.0 server - MSVC won't load these old format files.

Answer 2

I always liked the watch and trace feature: 'wt' -> It prints to the output window all the function calls as they happen. That was pretty cool stuff!