A quick comparison of the Series 5 with yesteryear's edition tells us ... very little actually. We'll need to put our spudgers to work mining for differences. To start with, here are the details we know:

LTPO OLED Retina display with Force Touch, optimized for always-on functionality

Custom-designed Apple 64-bit dual-core S5 SiP (System in Package)

Heart rate sensor and ECG

Comes in GPS-only or with optional LTE and brings a compass and ground elevation

Water resistance to a depth of 50 meters