I've been working on an HTML5 game for a year (http://ektomarch.com/games) with Chrome as my primary development target. When it launched, I'd get about 1 hour of battery life on a full charge while testing. Now, however, I'm getting about 4 hours. Flash still brings my battery down to around 2 hours at max.

Google's really put work into making javascript perform as well as possible, and it shows.