The FlexiShield Ultra-Thin case is one of the thinnest cases I've ever seen on a phone, it's hard to feel that there is a case on the phone which is great for me. When I buy a new phone I always need to have a case on it but I can't stand big bulky cases. It's really thin and perfectly clear so the only way you can ever really tell that there's a case on is if you look at the cut outs.
All cut outs for the case are clean, precise and smooth. With some cases you get a slightly sharp edge but not on this one. The case will not protect amazingly with falls but day to day it will do the job perfectly, slight edge so the screen doesn't touch a desk if put face down.
I have one complaint about the case and that is my worry of dirt or something from my pocket getting in between the case and plastic of the G4, due to it being a gel case it would move and potentially scratch the plastic. I haven't seen this yet but I have had to remove lint and dirt on a daily basis.
Overall, if you want a seriously thin case just to protect against light tumbles or scuffs from a desk this is brilliant but I'd look elsewhere for serious protection.