It would be useful to have also a real "instant pace" or be able to choose in which way the speed is expressed (km/h or min/km).
the Pace-discussion is one of the first features we discussed just when GH-615 was the actual model.
The problem is the acuracy of GPS. Especially when speeds are slow (like 10 or 12 km/h) there are big errors if the speed is calculated from two geographical points which are aquired within some seconds. These two points will be near together if the real speed is slow. Every point will have an absolute error up to 10 m caused by the GPS-accuracy.
There was the idea to calculate the Pace from the actual last 1000 m (called Pace1K-discussion) but at the end the GS-engineers managed to get a relative reliable value for pace, if the last 600 m were talken for pace-calgulation.
Instant-Pace as function 1/Speed would work, if you run speeds around 20 km/h = 3min/km.
Try the following: Ride your bike with constant 15/20/25 km measured by bycile-computer and watch the speed which is shown by the Gps-watch. GPS-watch will jump in a range which is larger, the slower you ride.
Certainly It would be fine to find a solution which eleminates the error caused by GPS-error at lower speeds but this would cost sensivity