The GC/GBA connectivity has been 'meh', but I would like to see the next-gen controllers have a screen or screen attachment. I like the concept of managing items or doing secondary actions without having to interrupt gameplay (see FF:CC). As stupid as the Nintendo DS is, the concept of having two screens doing separate things isn't bad. It just shouldn't be implemented on a portable system.
Of course, the screen controller (or screen attachment) must be packed in with the console, or else developers will never use the technology (see GC/GBA connectivity).
