Had the case for a few days now, and here are my thoughts.
I have the "scratch" or polishing effect at the top latch part as well. A bit annoying, but sounds like many bumper cases have this effect and it is not visible while the case is on. Still, not something I would expect given the amount of engineering that clearly went into the design.
The volume buttons are bit difficult to press as compared to the Apple OEM bumper which is a bit annoying especially now that you can use the volume button to take pictures. In response to one of the comments above, the antenna band is likely visible because the placement of the buttons are a bit higher on the original AT&T iPhone 4 and this allows universal fitment. I'd rather they move it though and also have something to make the buttons easier to press like what they do with the power button and what the Apple bumper case does there.
It is definitely slightly larger than the OEM bumper which is more curved than boxy. The material is different as well as it has a more plastic feel than rubbery feel.
The cutout at the bottom as others have mentioned will definitely cause issues with some connectors. In my car, the cable doesn't stay secure.
The lever is definitely secure when latched in. I posted these pictures on their facebook page.
Overall, I still like the case despite these flaws.