In my case, it wasn't a compiler bug - it was a bug in the STL, before the STL was part of the compiler. It was a separate thing you downloaded. I found a bug, and emailed Stepanov (or Lee - I forget). Me, just some random nobody on the internet. I got a fix, and then an improved fix, and then a final fix, all within two hours. I was floored.
Thankfully though we can still look at the STL source easily and presumably be able to determine the source of the bug or trace behavior or design test cases easier etc.
