I see NERDTree on your GVIM screenshot, yet no equivalent in Emacs. I don't know about you, but I missed NERDTree very much, so I looked at speedbar in Emacs. Unfortunately, out of the box it displays as another WM-level window (frame in Emacs parlance), but I managed to beat it into shape with: http://www.emacswiki.org/emacs/SrSpeedbar
Speedbar is good, because not only looks like NERDTree, it also displays summary of file contents (for programming: functions, classes, imports, etc.) if you want.
I try to move on to Emacs as my full time editor/IDE, but so far I failed, and I've been trying for several weeks now. The problem is that I put years of tinkering into my VIM to make it almost exactly as I need it. This means that I won't switch until Emacs has at least very similar number of customizations, macros, plugins, etc. And making this from scratch takes time. The only positive in this is that I already know what I want, so hopefully it'll take shorter than for the first time :)