I don't know about drag/drop, since I don't use that much, but it's easy to add panel applets for various things, including launching software and viewing directories. I usually just set up keyboard shortcuts for all my software using the Win key though. It's a lot faster than mousing over to the panel and clicking on an icon.
I just reinstalled it on my arch partition, they do now have that drag / drop to panel I mentioned, but it doesn't act like a dock still, so I had to put Cairo dock on. Going to toy with it some more tomorrow.
My use case is disjoint it seems. All I want is a pinnable launcher dock panel (preferrably with app integration, but that gets nutty), systemwide smart learning search with system key, a working system tray and clock, and decent multiheaded monitor support. None of the current Linux desktops really provide all those in tandem.
If Cairo does what you want out of a dock, then just use it alongside a regular Xfce panel for the system tray/clock. You can set up whatever system search software you want with an Xfce shortcut (in the Xfce settings). What problems are you having with multimonitor? I use ARandR to configure my monitors - again, in the Xfce settings, just set it to run when you hit the Fn key combo for monitor settings.