Question: In previous versions of IE developer tools you were able to open the source of CSS files in the debugger. 

This was of most use to verify that they had actually been downloaded / referenced correctly, ie if the request for a stylesheet returned a 404 error then thats the route cause of my styles not being applied.

However as of IE 11 the debugger no longer lists CSS files, so I can't use that to view their source and verify them.

I know that I can do this through the profiler - but that requires starting a profile trace and reloading the page, which is not exactly conducive to easy work flow. (Not to the frequent lock ups the F12 tools seem to experience on any of the profile tabs is used)

Is there still away through the dev tools to see the source of CSS files?

Answer: 
I don't believe so. There is a Connect issue reporting this and MS says they have it on their backlog for a "potential" future release. [IE11: CSS tab missing in new F12 Developer Tools](http://connect.microsoft.com/IE/feedback/details/811076/ie11-css-tab-missing-in-new-f12-developer-tools)

Update: Microsoft has announced via the [UserVoice site for Internet Explorer](https://wpdev.uservoice.com/forums/257854-internet-explorer-platform/suggestions/6595812-developer-tools-bring-back-css-tab-and-put-it-in) that they are planning on bringing it back.
I was surprised to discover this today, and resorted to using the Chrome F12 tool - Under the Resources Tab in the left hand panel you can expand Frames to access Images, Scripts and Stylesheets for your page - CSS are in the last of these of course.

It goes without saying that this only helps if you have access to Chrome and the site supports it.