If the previous page title is long, the back button shows "Back" instead of the previous page title.
What bothers me is that the "Back" text is not in the default language of the phone but always in English.
The obvious work-around to localize the "Back" text would be to change the long page title to the local translation of "Back" before calling the next page (that works) and change the page title back to the long title when the user returns to the previous page. Not very elegant.
It would be better to programmatically set the text of the back button.