Here's the thing, I like Neo because it has that slick look, that silicon membrane which is as thin as a paper that protects the phone and the feel on the case itself. However after realizing I have to clean the iPhone regularly every week, I need a case that I can easily detach and re-attach on the phone, Neo wasn't that case.
I tried Slider, way way back when they first released the white (annoying-you-can't-get-it-off version) and that's why I don't want to try it again anymore even though I've heard they fixed them already.
I wanted a case that I can take out regularly so I could clean the phone, while still showing it's real aesthetics. I went with the PS Clear Air jacket but found out that I need more protection from unexpected falls - that's when I leaned over to the Neo. Then Neo still acquired dust between the I & H frame and gave me a hard time putting it on and off so I leaned to a newer snap-type clear case - Griffin iClear. I can't remember if iClear is thinner than the slider, but it is definitely thinner than the Neo (probably because of the membrane they offer) and so far I could easily snap this case in and out in case dust came inside because of the two large openings. Now if you don't like large openings on a case, you could go to Neo my best bet, before the slider.
Yes dust is unavoidable. I tested how snug this case is before I even fully placed it on my phone. When I locked it in I couldn't really hear any movements, not even a millimeter that's why I was really happy about this case. So far I don't know why yours moved, that's probably how you got the scratches. If you'll watch itsmemorphious (on youtube) his review on this case actually shows as well that the phone doesn't move inside the case, proven and tested based on my experience.
Update as of 11/29/08
I accidentally dropped my iPhone after I washed my hands and I'm very lucky I had this case on. There were no scratches at the back or inside. The case never snapped open which was great. Good thing I had this case, highly recommended.