Default mode?

The default, or 'Normal' mode is what they felt was the best mix of power and economy for normal driving. It works very well for that, too. If you don't have to constantly climb hills give it a try, especially for mixed freeway and secondary road driving. Eco mode will still give better economy in stop and go driving, but Normal mode can give you great economy with less gas pedal effort when there is less traffic.

I couldn't find anything on that in the manual either. From playing with it, and from previously owning a 2005 Prius, I drew these conclusions:

1. Electric - Useless without add-in battery modification.
2. Eco - Sluggish but better gas mileage than 2005.
3. No Selection (default?) Performance and mileage same as 2005.
4. Power - Exceptional acceleration. Much quicker than 2005, great for passing at highway speeds, great for climbing hills from a dead stop.

The EV mode is useful for two kinds of driving: parking lot / traffic jam, where speeds don't exceed 20mph and acceleration is slow, and low-speed (less than 25mph) driving downhill or downslope. I've managed to get from the drugstore in town back home - about 1.5 miles - without using the engine, accelerating VERY gently up to 23mph and using the regen braking to its fullest. I ended up up with about 40% charge left in the traction battery pack. It isn't easy, though - the ICE will kick in at the drop of a toe. You have to have the climate control off, the defroster off, the heater off...