one thing you guys failed to mention: the 04-06 prii has has a thermos like bottle to keep the engine's hot coolant so that the next time you have a cold start, the wait for the engine to warm up is drastically decreased. By how much? I don't know maybe someone can provide this info?

The coolant can be kept hot for 6 hours or warm for 3 days... correct me if i'm wrong.

i got around 20 km a liter when i drove a civic 5 spd using advanced hypermiler techniques
and now I drive a salvage nwh20 prius that gets almost to 25 km/l with 195,000 km to date.