Appending to the end of the page title doesn't work, because the end of the title gets chopped off when it doesn't fit in the tab title or window title.
Prepending to the start of the page title does work though.
This is one of the reasons I use Twitter web client - it sits in a tab (on the @mentions screen) and I only pay attention to it when I see a "(1)" or whatever. It's unobtrusive notifications.
Prepending to the start of the page title does work though.