Having unique page titles within a space is a great idea as it avoids confusion and makes it really easy to link to a page. However...
If you could have an optional "display" or "alternate" title, you would be able to take advatage of other aspects of the system more readily.
The main example I am thinking of is using Confluence for software documentation and taking advantage of it's hierarchy view for class structures, etc.
The ability to show an alternate title in the hierarchy view would make it far more friendly to end-users IMHO. If no display/alternate title is given, default to page title on displays.
When viewing the page itself, or linking to a page, then the normal page title would be displayed.