When in focus assist mode you can zoom tight in to focus and then can move the point of focus around.
With the new firmware, it will remember where you left it, so you can check composition and return back to where you were focussing quickly and maybe leave it off centre if you want to take a series of portraits for instance.
I'm not sure if I'm the only one who complained that it used to forget where you were, but this is a boon for me and helps a lot when manually focussing on anything other than the central spot.