The problem with using the watt-hours number is resolution. If you are happy with the ~280 step gauge, then by all means you can continue to use that on
LEAFSCAN. However it's not for me, as I love seeing the SOC numbers tick down during my drive, and the 5 digit resolution is enough to even instantly see the effect using the climate control has on remaining energy. The "Gids" are just not a high enough resolution for me!
There are a lot of factors that are needed to "accurately" calculate range. For instance, cooler denser air will increase energy consumption, so you have to take that into account as well. For the same reason that Nissan was unable to create an accurate range estimator, we also have that problem. Seeing exactly how much energy is currently being used at all times and seeing how quickly your actions behind the wheel suck the pack dry allows your wetware upstairs to get a really good feel for range and also makes you a more efficient driver.
If someone can devise a good formula for displaying the usable energy in a higher resolution, I'll be happy to implement it. Maybe we can take the current capacity figure (amp hours with precision to the thousandths) and multiply that by corrected SOC and get a higher resolution watt-hours figure that both represents real energy (that will degrade over time) so you can "feel" it tick down.
-Phil