If you mean the hard shell it's actually kind of slippery. The problem with it is causes marks under the power and volume rockers. I still use it but I prefer no case.
I bought the Blackberry slider hard shell case and the one I had, the rubber buttons for the volume rockers kept pressing against the buttons on the device.
I rebooted the device with the case on it and I got the green Android guy with the red triangle of death and an error. I ended up taking the case off and the device was back to normal.
I took the case back to the AT&T store and got a refund. I have seen where a few folks have also had the same issue. Just thought I would pass it along.