its ICS not ICG. yes you should update to ICS. at first the battery will start to drain faster then GB but don't panic just after update turn off phone and take out the battery for like 20 mins and then get back on and recharge ur phone to 100%. this will sort out the battery issue. ICS will be updated to more newer versions as soon as new build releases. the current build u probably will be getting is 6.1.1.B.1.10 or if .54 shows up the better it is. 
PS: do not update to 6.1.1.C.1.10 yet because its not an official update.
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