I didn't buy mine from Google, so I didn't get the option of getting the insurance plan, but the only time I ever had to get a phone replaced was when my cell radio on my S4 basically just quit on me for no reason. VZW reps were just as perplexed by it as I was and they sent me out a replacement.
Not that I never drop my phone. Guess I've just been lucky. Only ever cracked the screen on my OG Droid.
I might look into a third-party insurance company. I forget the name of that one...Square Trade? Is that one?
Anyway, I'm planning to rock mine naked as well, if nothing else, at least at first. If I find I seem to be having trouble holding on to it, I may invest in a case, but I went with the aluminum because I like the different look from the phones I usually go for, so I want to show that off.