I consider myself to be an expert WinDbg user, when it comes to debugging
unmanaged x86 code. I haven't used WinDbg much on managed code, and when I did,
I found it quite painful.
Via Scott Guthrie's blog, I discovered
Tess Ferrandez's blog. Tess is an
escalation engineer in PSS who specializes in ASP.NET and a WinDbg virtuoso. Scott has a list of
her best posts.
Mind-blowing stuff, but not for the faint of heart.