"The only missing point in here is the selection of a window while in explode mode. Maybe there is a way, but I haven't found it yet."
Marc has nailed it here for me. On the rare occasions I use the 'exploded view' I want to be able to tab between the windows.
I mainly use Alt-Tab and Alt-backtick to move between applications and windows at present, but adding a keyboard mode for switching within the dash would help with organising workspaces by task irrespective of application...
Felipe here: I would also recommend another extension that provided window search abilities to the overview, so I could type "hacker news" or "handler.py" and go to the window I needed to, but it doesn't seem to be updated to gnome 3.6. I've been looking at the code and I can't figure out what is wrong with it.
This is actually an accessibility problem and as such it should just work by default (no extensions or anything). The difficulty is spending time to figure out the best way to do this as well as trying&developing the various solutions. I do hope it gets solved soon (GNOME 3.8 or 3.10).