Yes, I meant the case itself. I've never taken it off, including the bottom. I always just plug in the charger with the phone lying on my desk.
As for scratching the chrome when it slides out, I think that's the achilles heal of a sliding case. Dirt and dust are going to get inside no matter what. And when you slide the case out, dirt & dust are going to act like sand of a sandpaper.
When I take mine off, I'm going to try and wet it, maybe with rubbing alcohol and that might help it slide off.
I didn't do this but maybe this could work: paint a layer of lithium (or silicone) grease on the chrome before installing the case. The grease could act as a seal to prevent dirt and dust from getting in, and help it slide out later.