I used to send files or folders to USB flash-disks by droping them directly in the lateral pane of thunar 1.2. With Thunar 1.6, this is no longer possible (in fact external devices behave like local partitions). 
I think that bringing back drag n'drop to external devices wil be useful, as droping files to an icon in lateral pane is faster and easier than using "send to" in the right click menu.
Otherwise Thunar 1.6 is actually a huge improvement :)

Xubuntu 12.04 32 bit with Xfce 4.12 installed via ppa