Haven't got a TiBook any longer, but my friend tested it on a 500 MHz G4 Ti. There's an all-around speed improvement that anyone will see on their machines. There's also specific enhancements that users of specific machines will see, however.
Afaik, your TiBook does not support QuartzExtreme that well, for example, with its 16 MB VRAM. You still might see improvements there.
OpenGL has been much improved, I hear. But of course for the really new games, the graphics card, again, may be too low-end by now...
Boot and shutdown times have improved, but those are not that important with the 'books, as you rarely need to restart your 'book, anyway (keep it sleepin').