No, AFAIK no special mode is needed. I'm in Normal mode most of the time, unless I find a nifty corner where sport is more fun. ;] I can't find any real use for 'Eco' mode.
There's no difference in the way the car runs, the difference is in how you run the car.
Specifically I'm using mine like the throttle is an on/off switch. I've either got the throttle on the upper line between 'Eco & Power' (that's pulsing), or I'm on the lower line between 'Eco & Charge', that's gliding.
Simple as that. I'm either pulsing and gaining speed (to 5mph over the speed limit), or gliding and losing speed (to 5mph under the speed limit).
This of course is only for around town, haven't quite figured out how to apply it on the freeway, steady state throttle still seems best there, but I do now automatically 'glide' when a mile or so away from my exit on the freeway.
Certainly seems to be helping, but I need a ton more practice. It's kinda fun really. =]