Long post, sorry. I figured I could share my experience for other people who might come in the thread looking for advice on using the iPhone 6 naked.
I've been alternating between no case and Apple leather case, sometimes trying out the thin cases with clear/matte finish.
Right now I'm using my 6 Plus without a case, it's been approximately a month. (overall time I used the phone without a case is probably about 4 months total, I had the phone since early January)
Now, I'm the type of person that doesn't care too much about little scratches that can only be seen under direct sunlight, or dents that appear in the corners when you drop the phone accidentally or bang it up somewhere hard (all of which has happened to my phone already). As long as they aren't major and impact the visibility of the screen itself (or look way too ugly and used up overall) I am fine with it.
Screen: The phone will get little tiny scratches on the screen. I'm not hard on my phone, but I don't baby it either - just to clarify. I can't even tell they are there unless I view under direct sunlight.
Casing: If you happen to drop it, or apply too much pressure on it (I have some dents that somehow appeared from taking the phone out of really tight cases, the reason I stopped using cases other than the Apple leather case - I'm not imagining them either, as I almost lifted my fingernail from attempting to take the phone out out of a particularly tight thin case a few months ago. It's still healing) the phone can / will dent depending on the situation. Mostly in the corners. If you're very careful with the phone, however, this probably won't happen.
Camera: The protective ring around the lens might get scratched but the lens itself shouldn't be. I can't say too much on this subject since mine stays perfect and scratch-free. If you decide to go case-free and this worries you, just don't place the phone down on a hard surface as much as possible.
Conclusion?
That's all I can really say from my experience. I don't use my phone naked all the time, but hey. If you're the type of person who can't stand little nicks here and there on your phone, you probably shouldn't take the case off. Alternative option would be using the phone naked only when at home or indoors. I know some people who do that.
As for me, I just figured I should enjoy the beauty of the phone (and it's so thin!) while I use it, since I'm probably going to get a new phone in a year or two anyway. (I don't sell my old phones, so that factors in too.)
The fear of dropping it and shattering it does exist in the back of my mind - but as it is mostly a hit or miss situation depending on the point of impact of the drop regardless of the case availability (unless it's a real protective case, e.g. Otterbox) I decided to just go with it. I switch to Apple leather case when I'm going to a place where I can have the potential of dropping it more often than usual, just to be sure.
I realize that your main concern is the camera, which I can't really say much about. However, the camera should seriously be fine - the lens itself anyway, but that's the important part, no? Don't worry too much about it.
but my camera is fine. But I've only done it for a little less than a week.
