I decided to read all the reviews on Amazon, for the X100 batteries. The maximal Power brand is getting rave reviews for value and battery life, while the ostensibly OEM Fuji one is being panned as a counterfeit! Some also say it doesn't fit properly, etc. I'm surprised that Amazon continues to offer it, with such negative reviews, especially if it is really counterfeit.
I think I might try the Maximal Power brand.
“There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.”