The default dialog width is just a little bit too small, resulting in labels being truncated in most cases (at least here using German translation, maybe the same problem exists with other translations). With truncated I mean that the directory name is almost always cut off with triple dots "...". Please increase it by at least 50 pixels; that's not very much but improves the situation vastly.

An alternative approach would be to make the bold font a bit smaller.

commit 2635aa3b3b7cff2ae7ec0cc0561569e5d0a5f732
Author: Harald Judt <h.judt@gmx.at>
Date:   Sun Nov 25 13:09:15 2012 +0100

    Increase width of progress dialog size.

diff --git a/thunar/thunar-progress-dialog.c b/thunar/thunar-progress-dialog.c
index 00add6d..1fe2cfa 100644
--- a/thunar/thunar-progress-dialog.c
+++ b/thunar/thunar-progress-dialog.c
@@ -92,7 +92,7 @@ thunar_progress_dialog_init (ThunarProgressDialog *dialog)
   dialog->views = NULL;
 
   gtk_window_set_title (GTK_WINDOW (dialog), _("File Operation Progress"));
-  gtk_window_set_default_size (GTK_WINDOW (dialog), 400, 10);
+  gtk_window_set_default_size (GTK_WINDOW (dialog), 450, 10);
   gtk_window_set_modal (GTK_WINDOW (dialog), FALSE);
   gtk_window_set_transient_for (GTK_WINDOW (dialog), NULL);
   gtk_window_set_destroy_with_parent (GTK_WINDOW (dialog), FALSE);
@@ -264,7 +264,7 @@ thunar_progress_dialog_job_finished (ThunarProgressDialog *dialog,
   if (n_views < SCROLLVIEW_THRESHOLD)
     {
       /* try to shrink the window */
-      gtk_window_resize (GTK_WINDOW (dialog), 400, 10);
+      gtk_window_resize (GTK_WINDOW (dialog), 450, 10);
     }
 
   /* check if we still have at least one view */