GNOME Do's Docky theme, which provides a dock, sports a feature called "intellihide". This makes it only appear when the active window does not overlap the dock. I suppose xfce4-panel could implement this just as well - when there is no focused window covering the panel's area, the panel could be displayed, whereas it hides when you e.g. maximize an application. I'd consider this very useful.
I'll add my voice for this feature. At least all panels could be shown when showing only the desktop.
True, this would be a nice feature! (Wondering whether it's very costly to constantly poll whether there are windows overlapping the panel though...)
+1 on this one. This would really be appreciated, since e.g. for me, there ain't a better solution than the panel itself. It has all the features a dock misses, except for this one, which would make it a whole.
This has been implemented in the latest release (Xfce 4.12).
Indeed, a few years later and this is finally fixed :)