Gladly reporting that the battery life on the IS is extremely satisfactory considering the display and other capabilities.
Got the phone a couple of days back, the first day i charged fully.
The usual setting up of the phone, bluetooth transfers, internet via 3g & wi-fi, gaming, and of course the regualr calls & sms.
The battery lasted me over 13 hours.. still had 14% when i decided to charge again.
now with the usage a little lesser that the excitement has gone down a tad bit, the battery is really efficient.
close to a day (maybe more) with above average usage.
btw, also noticed the battery usage does not seem to vary much with the usage of any task killers