It's great that Luke Stackwalker displays source files, but this only works for locally built files. I often run binaries built on our build machines in which case the correct source file does not automatically show up. This could easily be fixed by using Source Server.
We already run source indexing on our build machine (http://randomascii.wordpress.com/2011/11/11/source-indexing-is-underused-awesomeness/) so that the information needed to retrieve source files from version control is embedded in the PDB. This article (http://msdn.microsoft.com/en-us/library/ms680641(VS.85).aspx) discusses how to use DbgHelp to retrieve source files using this information.
It's pretty cool and amazing and would make Luke Stackwalker significantly more polished for those who use source indexing (which should be everyone).
Contact me at valvesoftware.com, e-mail address bruced, if you want to discuss.