Jim,
I'm surprised you take her all the way to 0 miles! I don't think I'd have the stomach to try that. Your actual numbers look pretty similar to mine. If I drive strictly 65 mph (or a bit slower) on my 55 mile, mostly-freeway round-trip commute I will see 76 to 80 mile starting range after a couple of days. Now that I've driven a few months with the FFE, I find I have become less concerned with the range numbers as I know exactly how to raise and lower them with my driving choices and habits. I do have a hill that I have to climb both ways and I know my efficiency is reduced a little.
I use a spreadsheet to track battery capacity and that data appears to match yours. I think Ford sets Usable Capacity to ~85% of 23 kWh or 19.5 kWh. Here are some of my sample numbers below:
Date: 24-Sep-12
Mileage: 3615
Miles This Charge: 58.0
Average Efficiency (Wh/mile): 243
Total Energy (kWh): 14.1
Used Capacity (%): 72%
Estimated Capacity (kWh): 19.6
Date: 25-Sep-12
Mileage: 3670.8
Miles This Charge: 55.3
Average Efficiency (Wh/mile): 259
Total Energy (kWh): 14.3
Used Capacity (%): 74%
Estimated Capacity (kWh): 19.3
Tim