It's not too bad, but it does require a little force to get over the hold that the case has on the phone. When I first pulled the case out of the packaging, the top and bottom didn't stay together at all, which confused me. If you grabbed the case by the top, the bottom piece would slide off of it.
However, the two pieces closed around the phone form a nice seal that keeps everything together, but also makes it slightly difficult to get the bottom off. It's a little easier if you seesaw the pulling from one side to the other, then it comes off without much trouble.
I don't see anything that would be causing scratches, but I haven't been able to get my hands on a dock yet so I haven't been taking the bottom off and on very much.
I only remember one other case that had a removable bottom part for dock accessibility - it was a plastic case where the bottom part folded backwards for dock access. It may have been a bit easier for docking, but the case felt extremely cheap to me. For the record, it was a thin white plastic, but supposedly they also made a black version.
I've messed with several cases at the store and seen a few my friend had gotten, and this one is my favorite so far.