I bought the Otterbox Commuter case the same day I bought my DRM. I got it from Amazon so I had to wait a few days to get it. It's been on my phone since I got it (3 months) and I don't even notice the size difference anymore. It still fits in my pocket perfectly, and the Commuter case is a slick plastic, not a rubbery outer so it slides in and out of my pocket. I've droped my phone getting in and out of my car a few times, directly on to the pavement. The phone is still in brand new condition. Even the case is still near perfect, with only a couple small scratches. I highly recommend the Otterbox Commuter case. The Defender is a little too bulky and expensive for me.
You can still get it on Amazon for almost half the price that Otterbox sells it for on their site.
Amazon.com: OtterBox Commuter Series for Driod Razr MAXX by Motorola: Cell Phones & Accessories