I'm in exactly the same position. Left the phone in to charge overnight and woke up friday morning to a phone that was nearly out of juice. I have tried the SIM out hard reset trick but nothing. The phone is insured but this seems to be an inherent fault with this model.
Not sure about the rest of you but my option is to get it fixed, sell it as a clean phone and go back to Iphone were I had no issues in the 2 1/2 years with my 3GS. Why did I change!!!