IMHO, navigation buttons in Toolbar style (Go to previous, Go to next, Open the parent...) are also useful in Pathbar style. For example: 1) Open $HOME/sources/xfce/thunar 2) Click shortcut in side pane (e.g. $HOME/packages/xfce/). 3) I want to go back to $HOME/sources/xfce/thunar In this case, "Go to the previous visited folder" button is useful and IMHO this is not rare case.
I would find this feature useful, too.
It was, I think unintentionally, fixed during the GTK3 port, available in 1.7.0.