My wife was the first one to notice that her Key Fob was dying over the summer. So we switched keys because everytime she'd try to show me it wasn't working, it'd work.
Anyways, it took a couple weeks, but it finally started acting up for me as well. I noticed it starting when I had to mash really hard on the key fob button to get the car to unlock from the other side of the parking lot.
Over time, I started having more and more trouble un/locking the car from the button on the handle. I found out if you're having trouble getting the car to detect the keyfob when you push the button on the door handles, then push a button on the keyfob, and the car should detect the key, and allow you to un/lock the car with the button on the door.
On a side note, I'm going to go get a new set of batteries while Azumi's getting her oil changed today. Thanks for posting the battery guys. It helps a bunch!