A lot of users seem to be wondering how to edit keyboard shortcuts in xfce4-terminal 0.6.x. The built-in shortcut editor is indeed gone and the application now uses editable GTK+ accelerators like other GTK+ applications. This is more consistent and allows to drop the exo dependency which makes the application lighter.

The FAQ of the Xfce documentation has a guide on how to edit GTK+ accelerators of xfce4-terminal. You'll get your custom shortcuts back in no time!

PS: xfce4-terminal 0.6.1 is out and has a killer "drop-down" mode ala guake / tilda. See Nick's Google+ page for screenshots.