If you do not want a damaged iPhone you are certainly using the wrong case. Agent 18 cases are JUNK. They allow debris to lodge between your phone and the case. They reek havoc on the shiny chrome. If you love your iPhone please do not intrust it to AGENT 18! Mark
Personally, I have had 3 cases and one skin for my V1 and the one I ended up with is the incase slider. Loved it so much I bought one today for my 3G. No scratching, great protection.
I use the white one because it looks clean and doesn't show finger prints like the black gloss does. There are apparently some new ones coming out and there is also a black rubberized matte finish as well.
I also picked up the DLO Static anti-glare screen protector 5 pack. There is a slight problem with the case pushing against the screen protector, but i fixed that by shaving .01mm off the edges of the case that cover the bezel and it's perfect now.
On the V1, I used the Crystal Support anti-glare and the Slider with no problems.
The Incase Slider and the Seidio Innocase II can't really use a screen protector with it. If you need to use a screen protector get the Agent 18, but clean it regularly so the dust doesn't get trapped in the case to much.