I've driven my i now all of 2 days. It looks like I'll be getting about 70 miles out of a charge, assuming a linear monitor level. The charge level indicator has 16 bars, and that's 4-5 miles per bar. I keep seeing posts that say "range remaining." I don't have that, probably because I have an ES. So I count bars.
The driving I do is relatively rural... mostly 25-50 mph on roads with ups & downs and curves. The first/last 6 miles of my daily commute is 2000' of altitude loss/gain. I go down mostly in Eco mode with a little B, and appear to use zero power for the first 13 miles of my commute. When I go back up, it takes 3-4 bars, a quarter of a charge. My daily jaunt is 30-40 mi and I drive conservatively.
It took me a little while to get used to the drive modes. There is no good information about when to use which mode. I wrongly assumed at first that B mode would provide the best economy no matter what. In fact, B mode seems to use far more power than D mode in certain conditions, such as a consistent hill climb. Eco and B mode reduce forward momentum. So when you need to retain that forward momentum, such as uphill or higher speeds, you use more power to work against Eco and B mode. Eco mode is great for stop/go driving. B mode seems useful primarily if you want to use the engine as a brake, going down hill.
So it looks like I should have included brakes into my cost saving calculations. In my gas vehicle I need new brakes every other year.