More specifically: I would like to easily see if a request is XHR. Without having to open the detail panel and look for hints there. Maybe we can do soemthing similar to what the Chrome dev tools do, where you can filter on: Documents, Stylesheets, Images, Scripts, XHR, Fonts, WebSockets, Other.
I don't think we need a new column just for this, but we could maybe add an option to show it. I'll change bug 862855 to add the ability of showing more columns. Bug 859046 takes care of filtering.