As my third Impreza and second STI, this is definitely my favorite Subaru. The ride is smoother than the 05 model and generally feels more refined. The interior has plenty of little features I'd be wishing for in the previous iterations.
As a GPS virgin, the nav system is by far my favorite toy at the moment. The novelty of it will eventually wear off and when it does I doubt the plus of GPS will offset the lack of a multi-disc in dash CD player.
With the complete removal of the ashtray, I find myself without a place to dump spare change that I like to have on hand for parking and car washes. Height adjustable passenger seasts would be nice plus as passengers often complain of feeling low in that seat.