I've gone for the dark Spigen Slim Armor. I'm not sure if I'll stick with this or not - I think the much cheaper Thin Fit looks best of all the Spigen G4 cases. I decided to get one with a stand, but I have a feeling I'll end up getting the Thin Fit for most day-to-day use.
[edit] A couple of days on, and I like it. It has a weird effect though. The phone by itself looks slim and feels light. The case by itself feels light. But you put the two together, and somehow it feels very weighty, and like something you could use to kill a man. I think it's entirely psychological because of the difference in shape, and that the naked G4 feels a little flimsy because of the flexible removeable back, whereas the edges and hard material of the Spigen case tell your brain that you're holding something much more substantial. It's also different ergonomically because of the rubber rim which prevents the screen from ever hitting the floor if you drop it, since your finger now butts up against that when you're close to the screen edge.
Although it's designed as an outdoor case, I can see myself going the other way with it and putting the case on when I know I'll be using it with the prop.