The back of mine doesn't seem to go on as snugly as it used to. I've swapped the battery a few times since getting mine on launch day. Probably 10 or so times. If i press lightly with my thumb on the center of the bottom part of the back, it makes a squeaky noise and definitely gives. I'm used to backs that are made to come off the phone a bit more easily (blackberrys, moto droid), so I've always found the plastic tabs on the inc kind of suboptimal. I guess that's one of the sacrifices you make for a super slim and light phone. I ordered a new back cover from ebay, hopefully that will give me back that tight-as-a-drum new phone feel.