So let me see if i understand this correctly. you said after 12hours of standby you had 9% battery left? or did it use 9% leaving you with about 91% Battery? A normal day for me is 15 to 18 hours of standby and about 3 to 4 hours of use, At the end of the day i end up with about 50% battery left, give or take a few percentages. My phone activity is phone calls, texting, facebook, and i have several forums like this one. I have noticed when using a forum app my battery drains kinda fast. Other apps Like the stock ones apple puts on your phone does not drain my battery any where near as fast.
As for updating to iSO 5.0.1 is up to you, Rumor has it that another update iSO 5.0.2 is coming before the end of next week. Don't take my word for that, I have read several websites that claim this but i can't comfirm it. That rumor is claiming to give the 4s 40 hours of standby and 10 hours of usage. Now that is very wishfull thinking, and i hope that it is true. We will just have to wait and see.
With that being said use your own judgement on updating to iSO 5.0.1. I personally didn't see much if any difference at all after updating.